feat: add value_bitmask_filter to the read API

[mutianf]

Manually generate the bitmask filter proto to unblock critical proto generation.

[gemini-code-assist]

Code Review

This pull request introduces the ValueBitmask feature to the Google Cloud Bigtable V2 client, adding the ValueBitmask message type and integrating it into row filters. The PR also includes extensive refactoring, such as import reordering and whitespace adjustments. Feedback was provided to separate these non-critical refactorings into a dedicated pull request to maintain focus and improve the review process.

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packages/google-cloud-bigtable/google/cloud/bigtable_v2/init.py (19)

This pull request includes extensive non-critical refactoring, such as import reordering and whitespace adjustments. Please move these changes to a separate pull request to keep this one focused on the value_bitmask_filter feature and to simplify the review process.

References

1. Defer non-critical refactoring or cleanup tasks to a separate pull request to maintain the focus and reviewability of the current one.