Fix exists method to support using Requester Pays

[kylase]

• Fix exists method to support user_project for Requester Pays
• Corrected minor grammatical errors in docstrings

related: #32760

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[kylase]

@potiuk, how do I get a reviewer or who can I reach out to review this PR? I notice that the google provider has no CODEOWNER.

[VladaZakharova]

Hi! I see that you have added unit test, but can you please provide here a screenshot of successfully executed system test for this logic? Thanks!

[potiuk]

Hi! I see that you have added unit test, but can you please provide here a screenshot of successfully executed system test for this logic? Thanks!

I am not sure if people run those :) -> but @kylase -> maybe you can? It's not difficult -> https://github.com/apache/airflow/blob/main/contributing-docs/testing/system_tests.rst

[kylase]

I did run the system tests prior to submitting a PR.

Sorry, I have been busy these days, so I wasn't able to respond.

I will provide a screenshot by next week.

[potiuk]

No need in this case - we trust you :)

[kylase]

@potiuk and @VladaZakharova, sorry for the delay.