Fix pending SSL data handling in stream client

[mihirduvedi]

What type of PR is this?

/kind bug

What this PR does / why we need it:

WSClient.update() can wait on poll() or select() even when an SSL socket already has decrypted data buffered internally. This can delay stream output indefinitely when no additional network event arrives.

This change checks SSLSocket.pending() before polling and immediately processes a WebSocket frame when buffered SSL data is available. It also adds a deterministic regression test using timeout=None that verifies neither polling path is entered.

Which issue(s) this PR fixes:

Fixes #2414

Special notes for your reviewer:

This addresses the unit-test request from #2422 and the review feedback to avoid calling poll() or select() when SSL data is already pending.

Tests:

• python -m pytest -q kubernetes/base/stream/ws_client_test.py — 17 passed
• python -m pytest -q kubernetes/base --ignore=kubernetes/base/dynamic/test_client.py --ignore=kubernetes/base/dynamic/test_discovery.py — 143 passed

The two excluded dynamic-client modules require a live Kubernetes cluster.

Does this PR introduce a user-facing change?

Fixed stream operations over SSL to process buffered WebSocket data without waiting for another socket event.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: mihirduvedi / name: mihirduvedi (730aa78)

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mihirduvedi
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