Allow nativeparse to parse source code directly

[bzoracler]

This is the mypy counterpart of mypyc/ast_serialize#54

[bzoracler]

Current CI failure is due to changed typing signature of ast_serialize.parse::source, this has been fixed in the corresponding PR in mypyc/ast_serialize (see changed line).

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[bzoracler]

CI failures:

• Step Compiled with_mypyc: As before, this is fixed in https://github.com/bzoracler/ast_serialize/blob/566ddc362930a821549ca5fbb0d7d0f3bd88eb6e/ast_serialize.pyi#L26
• These errors should be fixed using the updated binaries built from the changes in Allow parsing source code directly mypyc/ast_serialize#54:
  • E TypeError: argument 'source': 'bytes' object is not an instance of 'str'
  • E ValueError: Source parsing is not supported yet for test_trivial_binary_data_from_string_source
  • E ValueError: Source parsing is not supported yet for testPackageRootMultipleParallel, testParallelRunWithSyntaxError, testCheckingStubPackagesWorksInParallelMode, and job Parallel tests with .*: I believe like the code path for parallel checking causes both the source code and a file name to be passed to parsing functions? I think the tests passed before because either the source argument was not passed or the file_exists check resulted in False (and we fell back to the old parser when the file didn't exist).

Is it possible for CI to run a non-released version of ast_serialize?