Disable deprecated member findings in generated code

People might want to mock classes that use some deprecated libraries
or classes. Mocked class itself could also be deprecated. Deprecated
member findings for the generated code are not very useful:

1. They are dubbing the finding in the actual code.
2. They are hard to disable (have to edit generated code).

So disable `deprecated_member_use` and `deprecated_member_use_from_same_package`
findings in the generated code.

Fixes #565

PiperOrigin-RevId: 548118939

lib/src/builder.dart

@@ -97,6 +97,10 @@ class MockBuilder implements Builder {
       b.body.add(Code('// ignore_for_file: avoid_setters_without_getters\n'));
       // We don't properly prefix imported class names in doc comments.
       b.body.add(Code('// ignore_for_file: comment_references\n'));
+      // We might import a deprecated library, or implement a deprecated class.
+      b.body.add(Code('// ignore_for_file: deprecated_member_use\n'));
+      b.body.add(Code(
+          '// ignore_for_file: deprecated_member_use_from_same_package\n'));
       // We might import a package's 'src' directory.
       b.body.add(Code('// ignore_for_file: implementation_imports\n'));
       // `Mock.noSuchMethod` is `@visibleForTesting`, but the generated code is