Fix warnings generated by Clang-Tidy (#8181)

* Remove unused namespace alias.

* Remove unused 'using' statements.

* Remove more unused 'using' and namspace aliases.

* Prefer absl::StrContains over comparing `find` result with `npos`.

* Remove more unused things.

* Prefer usage of `empty()` over `size()` when possible.

* Remove more unused things.

* Address code review.

* Address code review.

* More fixes to query_core.cc

* comment should match parameter name.

* Pre-allocate container capacity for better performance.

* More fixes.

* Fix inconsistent declaration parameter name.

* Fix inconsistent declaration parameter name.

* Fix inconsistent declaration parameter name.

* Address bugprone-inaccurate-erase (inappropriate `erase` overload was used).

* Fix return type of move and copy constructor.

* Fix bugprone use after move.

* Fix formatting.

* Reflect the param name change in the doc.

Author: ehsannas

Firestore/Example/Tests/API/FIRQuerySnapshotTests.mm

@@ -37,7 +37,6 @@
 #include "Firestore/core/src/util/string_apple.h"
 #include "Firestore/core/test/unit/testutil/testutil.h"
 
-namespace util = firebase::firestore::util;
 namespace testutil = firebase::firestore::testutil;
 
 using firebase::firestore::api::DocumentChange;

Firestore/Example/Tests/API/FSTAPIHelpers.mm

@@ -52,7 +52,6 @@
 using firebase::firestore::model::DocumentSet;
 using firebase::firestore::model::DocumentState;
 using firebase::firestore::model::FieldValue;
-using firebase::firestore::model::NoDocument;
 
 using testutil::Doc;
 using testutil::Query;

Firestore/Example/Tests/Integration/FSTDatastoreTests.mm

@@ -65,15 +65,11 @@
 using firebase::firestore::local::MemoryPersistence;
 using firebase::firestore::local::Persistence;
 using firebase::firestore::local::QueryEngine;
-using firebase::firestore::local::TargetData;
 using firebase::firestore::model::BatchId;
 using firebase::firestore::model::DatabaseId;
-using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::DocumentKeySet;
-using firebase::firestore::model::FieldValue;
 using firebase::firestore::model::MutationBatch;
 using firebase::firestore::model::MutationBatchResult;
-using firebase::firestore::model::Precondition;
 using firebase::firestore::model::OnlineState;
 using firebase::firestore::model::TargetId;
 using firebase::firestore::remote::ConnectivityMonitor;
@@ -86,7 +82,6 @@
 using firebase::firestore::remote::RemoteStore;
 using firebase::firestore::remote::RemoteStoreCallback;
 using firebase::firestore::testutil::Map;
-using firebase::firestore::testutil::WrapObject;
 using firebase::firestore::util::AsyncQueue;
 using firebase::firestore::util::Status;
 

Firestore/Example/Tests/SpecTests/FSTSyncEngineTestDriver.h

@@ -53,7 +53,6 @@ namespace bundle = firebase::firestore::bundle;
 namespace core = firebase::firestore::core;
 namespace local = firebase::firestore::local;
 namespace model = firebase::firestore::model;
-namespace nanopb = firebase::firestore::nanopb;
 namespace remote = firebase::firestore::remote;
 namespace util = firebase::firestore::util;
 

Firestore/Example/Tests/Util/FSTHelpers.mm

@@ -40,7 +40,6 @@
 using firebase::firestore::model::DatabaseId;
 using firebase::firestore::model::DeleteMutation;
 using firebase::firestore::model::DocumentKey;
-using firebase::firestore::model::FieldMask;
 using firebase::firestore::model::FieldPath;
 using firebase::firestore::model::FieldValue;
 using firebase::firestore::model::ObjectValue;

Firestore/Example/Tests/Util/FSTIntegrationTestCase.mm

@@ -52,17 +52,14 @@
 #include "Firestore/core/test/unit/testutil/status_testing.h"
 #include "absl/memory/memory.h"
 
-namespace testutil = firebase::firestore::testutil;
 namespace util = firebase::firestore::util;
 
 using firebase::firestore::auth::CredentialChangeListener;
-using firebase::firestore::auth::CredentialsProvider;
 using firebase::firestore::auth::EmptyCredentialsProvider;
 using firebase::firestore::auth::User;
 using firebase::firestore::core::DatabaseInfo;
 using firebase::firestore::local::LevelDbOpener;
 using firebase::firestore::model::DatabaseId;
-using firebase::firestore::remote::GrpcConnection;
 using firebase::firestore::remote::FirebaseMetadataProviderApple;
 using firebase::firestore::testutil::AppForUnitTesting;
 using firebase::firestore::testutil::AsyncQueueForTesting;

Firestore/Source/API/FIRDocumentReference.mm

@@ -59,7 +59,6 @@
 using firebase::firestore::core::ParsedUpdateData;
 using firebase::firestore::model::DocumentKey;
 using firebase::firestore::model::ResourcePath;
-using firebase::firestore::util::Status;
 using firebase::firestore::util::StatusOr;
 using firebase::firestore::util::StatusOrCallback;
 using firebase::firestore::util::ThrowInvalidArgument;

Firestore/Source/API/FIRDocumentSnapshot.mm

@@ -45,8 +45,6 @@
 #include "Firestore/core/src/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
-using firebase::Timestamp;
-using firebase::firestore::GeoPoint;
 using firebase::firestore::api::DocumentSnapshot;
 using firebase::firestore::api::Firestore;
 using firebase::firestore::api::MakeFIRGeoPoint;

Firestore/Source/API/FIRLoadBundleTask.mm

@@ -27,8 +27,6 @@
 
 namespace {
 
-namespace api = firebase::firestore::api;
-namespace util = firebase::firestore::util;
 using firebase::firestore::util::ThrowInvalidArgument;
 
 }  // namespace

Firestore/Source/API/FIRQuery.mm

@@ -55,10 +55,10 @@
 #include "Firestore/core/src/util/statusor.h"
 #include "Firestore/core/src/util/string_apple.h"
 #include "absl/memory/memory.h"
+#include "absl/strings/match.h"
 
 namespace util = firebase::firestore::util;
 using firebase::firestore::api::Firestore;
-using firebase::firestore::api::ListenerRegistration;
 using firebase::firestore::api::Query;
 using firebase::firestore::api::QueryListenerRegistration;
 using firebase::firestore::api::QuerySnapshot;
@@ -592,7 +592,7 @@ - (Bound)boundFromFieldValues:(NSArray<id> *)fieldValues isBefore:(BOOL)isBefore
         ThrowInvalidArgument("Invalid query. Expected a string for the document ID.");
       }
       const std::string &documentID = fieldValue.string_value();
-      if (!self.query.IsCollectionGroupQuery() && documentID.find('/') != std::string::npos) {
+      if (!self.query.IsCollectionGroupQuery() && absl::StrContains(documentID, "/")) {
         ThrowInvalidArgument("Invalid query. When querying a collection and ordering by document "
                              "ID, you must pass a plain document ID, but '%s' contains a slash.",
                              documentID);