Bigquery proxy support

[mansfieldj3]

Adds support for supplying a HTTP / HTTPS proxy to the bigquery hook using any of

1. connection form widgets
2. As a field in the hook itself as a string i.e. BigQueryHook(http_proxy="http://proxy:8080")
3. As part of the connection extras i.e. "http_proxy": "http://proxy:8080"

• closes: Google Cloud Connection support for non-environmental proxy #64278

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Generated-by: Claude Sonnet 4.6 following the guidelines

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[mansfieldj3]

As an FYI, when testing in my environment the code was reformatted by Ruff which considerably expands the number of changes, if this is an issue, please let me know and I'll revert this

[mansfieldj3]

Should be ready for review (assuming it passes the checks)

[mansfieldj3]

@shahar1 can you review this when you get the chance?

[shahar1]

As an FYI, when testing in my environment the code was reformatted by Ruff which considerably expands the number of changes, if this is an issue, please let me know and I'll revert this

Could you please revert the extra formatting? It makes it hard to review, thanks!

[mansfieldj3]

Figured that might be the case, I'll try and update the request to revert the formatting sometime either tomorrow or early next week

[mansfieldj3]

I think I've moved over the functional changes without touching the rest of the formatting, I just need to confirm it still works in my env after this

[mansfieldj3]

Just confirming the revised version still works as intended in my environment @shahar1

[shahar1]

Thanks for your contribution! I have a couple of comments - there's some rework to be done, mainly to make the changes minimal and precise as much as possible.
If possible, I'd like to ask adding a Dag example + a screenshot that demonstrates that the Dag can run E2E. If you're unable to do so, please provide instructions for others to do so.

[mansfieldj3]

Cut down unit tests, consolidated imports, reversed changes to method that wasn't needed, and added dialect / kwargs / timeout changes + tested to confirm everything was still working on my end obvs

[mansfieldj3]

Need to rework the unit tests. Bugger.