Test hash validation also for upload by path

[nsoranzo]

Also:

• Add some related type annotations

Questions / future work:

1. Currently setting validate_hashes to True in the request is required, I think we should just validate the hashes if they are part of the request
2. If a hash doesn't validate, we currently only add an error_message but the dataset state remains ok, seems wrong to me?

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[jdavcs]

lgtm