increase grpc timeouts & force seq exec (#34739)

[A1K28]

Increase GRPC timeouts and force sequential execution for increased stability. you can see successful runs here: https://github.com/A1K28/beam/actions/workflows/beam_PreCommit_Python.yml

fixes #34739

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[A1K28]

@Amar3tto

[A1K28]

R: @damccorm

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[damccorm]

Thanks! Had one question, but doesn't need to block merging

[damccorm]

How do these Beam-specific config settings impact things? I can't see where they are used

[A1K28]

My apologies, I was supposed to implement these in the code. I will fix this in the next PR. Currently, you are right, they don't do anything, since i didn't write necessary code for it.

[damccorm]

No problem - I was guessing that was the case; since we merged it we'll be able to see the impact in any PR workflow runs which is nice anyways