refactor: simplify source generator tests assertions #1557

Job	Run time
Mutation tests	6m 51s
API tests	3m 23s
Unit tests (macos-latest)	4m 54s
Static code analysis	5m 39s
Unit tests (windows-latest)	8m 23s
Benchmarks (CompleteEventBenchmarks)	2m 48s
Unit tests (ubuntu-latest)	4m 4s
Benchmarks (CompletePropertyBenchmarks)	4m 13s
Benchmarks (CompleteMethodBenchmarks)	4m 49s
Benchmarks (CompleteIndexerBenchmarks)	3m 58s
Benchmarks (CallbackBenchmarks)	2m 50s
Publish Tests Results	29s
	52m 21s

Provide feedback