[proto] add block query APIs (#85)

#### Type of change

- New feature

#### Description

This commits adds the following four gRPC APIs
```go
    rpc GetBlockchainInfo(google.protobuf.Empty) returns (common.BlockchainInfo);
    rpc GetBlockByNumber(BlockNumber) returns (common.Block);
    rpc GetBlockByTxID(TxID) returns (common.Block);
    rpc GetTxByID(TxID) returns (common.Envelope);
```

to be exposed by the sidecar to allow endorser/fsc to query block or tx
envelope from the ledger store.

Signed-off-by: Senthilnathan <cendhu@gmail.com>

Author: cendhu

Makefile

@@ -119,6 +119,10 @@ proto: FORCE $(PROTOS_SENTINEL)
 		-I="${PROTOS_DIR}" \
 		--go_opt=Mmsp/msp_config.proto=github.com/hyperledger/fabric-protos-go-apiv2/msp \
         --go-grpc_opt=Mmsp/msp_config.proto=github.com/hyperledger/fabric-protos-go-apiv2/msp \
+		--go_opt=Mcommon/common.proto=github.com/hyperledger/fabric-protos-go-apiv2/common \
+		--go_opt=Mcommon/ledger.proto=github.com/hyperledger/fabric-protos-go-apiv2/common \
+		--go-grpc_opt=Mcommon/common.proto=github.com/hyperledger/fabric-protos-go-apiv2/common \
+		--go-grpc_opt=Mcommon/ledger.proto=github.com/hyperledger/fabric-protos-go-apiv2/common \
 		--go-grpc_out=. \
 		--go-grpc_opt=paths=source_relative \
 		--go_out=paths=source_relative:. \

api/committerpb/block_query.pb.go

@@ -0,0 +1,31 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+syntax = "proto3";
+
+option go_package = "github.com/hyperledger/fabric-x-common/api/committerpb";
+
+package committerpb;
+
+import "google/protobuf/empty.proto";
+import "common/common.proto";
+import "common/ledger.proto";
+
+// BlockQueryService provides read-only access to the block store ledger.
+service BlockQueryService {
+    rpc GetBlockchainInfo(google.protobuf.Empty) returns (common.BlockchainInfo);
+    rpc GetBlockByNumber(BlockNumber) returns (common.Block);
+    rpc GetBlockByTxID(TxID) returns (common.Block);
+    rpc GetTxByID(TxID) returns (common.Envelope);
+}
+
+message BlockNumber {
+    uint64 number = 1;
+}
+
+message TxID {
+    string tx_id = 1;
+}