Generate modifier getters/setters for ExecutableFragmentImpl,FieldFragmentImpl, FormalParameterFragmentImpl, FragmentImpl, InterfaceFragmentImpl, MixinFragmentImpl, NonParameterVariableFragmentImpl, and TypeAliasFragmentImpl.

Make generated mixins include their own `hasModifier` and `setModifier`.

Create modifier `HAS_IMPLICIT_RETURN_TYPE`, rename modifier `COVARIANT`
to `EXPLICITLY_COVARIANT` to make it more precise.

Change-Id: I92d4b72949a6f03ef0b1b03f92abcf848545f2a2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/445400
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: fshcheglov

pkg/analyzer/lib/src/dart/analysis/driver.dart

@@ -109,7 +109,7 @@ testFineAfterLibraryAnalyzerHook;
 // TODO(scheglov): Clean up the list of implicitly analyzed files.
 class AnalysisDriver {
   /// The version of data format, should be incremented on every format change.
-  static const int DATA_VERSION = 515;
+  static const int DATA_VERSION = 517;
 
   /// The number of exception contexts allowed to write. Once this field is
   /// zero, we stop writing any new exception contexts in this process.