Try to open file in UploadCompletionHook initializer with given path to ensure file upload works

[DylanRussell]

Description

Make a change to try to open a file in UploadCompletionHook initializer with the given path in the given format to ensure file upload works, if it fails raise an error...

The current implementation doesn't check the path, lets a bad path get passed in, and then when the upload hook is invoked we repeatedly fail.. Better to check if things are working upfront and throw a more understandable error..

Type of change

Please delete options that are not relevant.

• [x ] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Unit tests.. Tested locally by running the following code:

import fsspec, posixpath
_format="jsonl"
_content_type = (
            "application/json"
            if _format == "json"
            else "application/jsonl"
        )
base_path = "gs://my-bucket-name"
_fs, base_path = fsspec.url_to_fs(base_path)
base_path = _fs.unstrip_protocol(base_path)
test_path = posixpath.join(
    base_path,
    f".one_off_test_to_see_if_upload_works.{_format}",
)

with _fs.open(
    test_path, "w", content_type=_content_type
) as file:
  file.write("\n")
_fs.rm_file(test_path)

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• [X ] No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• [ X] Followed the style guidelines of this project
• [ X] Changelogs have been updated
• [ X] Unit tests have been added
• [ X] Documentation has been updated