Make sure stale file handler doesn't crash the DagFileProcessorManager

[dabla]

As described in issue #69321, this PR makes sure a stale file handler doesn't crash the DagFileProcessorManager. The OSError should be catched and logged as warning instead.

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Claude Opus 4.6

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[SameerMesiah97]

Looks good. Just one nit if you want to address it.

[potiuk]

Approving — small, correctly-scoped fix for the stale-NFS-handle crash in #69321. Routing all three logger_filehandle.close() sites through a close() that swallows OSError is the right call, and reaching for LoggingMixin's self.log rather than self.process_log (which writes through the very handle that just went stale) is a nice touch.

A couple of non-blocking nits:

1. One inline comment on the terminate_orphan_processes test — it mocks the whole processor, so it doesn't actually exercise the OSError swallow (the other two tests do).
2. The commit subjects use refactor: Conventional-Commit prefixes, which Airflow disallows (check-no-conventional-commit-message). It's a commit-msg-stage hook so it isn't gating CI, and the squash-merge uses the clean PR title — but worth rewording/squashing to keep history tidy.

Optional follow-up (out of scope here): a stale handle can also raise on writes via structlog.BytesLogger, not just on close — worth keeping in mind if the crash recurs from a different frame.

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[potiuk]

rebased it as well - fell free to merge with/without nit

[dabla]

rebased it as well - fell free to merge with/without nit

Thanks for the review @potiuk will fix nits before merging.