Fix STDIN consumption in alias groups for eval-file

[Copilot]

Fix STDIN input with alias groups for eval-file command

• Add static cache property to store STDIN contents
• Modify execute_eval method to cache STDIN on first read
• Use STDIN inode+device as cache key for cross-process sharing
• Reuse cached STDIN for subsequent reads in alias groups
• Add automatic cleanup of stale cache files (older than 1 hour)
• Fallback to parent PID or environment variable when fstat unavailable
• Pass all code quality checks (lint, phpcs, phpstan)
• Fix test to verify STDIN executes on both sites in alias group
• Fix cache sharing issue - all subprocesses now share the same cache file

Original prompt

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This section details on the original issue you should resolve

<issue_title>Input from STDIN does not work with an alias group</issue_title>
<issue_description>cat cleanup_stuff.php | wp @site_a eval-file - works.
But it does not work if used with a alias group.
It only triggers on the first entry of the alias group.

</issue_description>

Comments on the Issue (you are @copilot in this section)

@janw-me I also took alook at the output when adding the `--debug` flag. I'm willing to look into it but am uncertain where to start. @janw-me PS a dirty hack workaround I found out is misusing the regular `eval` command:

wp @blueprint eval "$(tail -n +2 cleanup.php )"</comment_new>
<comment_new>@schlessera
Oh, I assume STDIN is being read per site for the group, so after the first run, the empty STDIN is being read.

Not sure how we should go about for this, I'll have to do a bit of exploration here.</comment_new>

• Fixes Input from STDIN does not work with an alias group #52

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[codecov]

Codecov Report

❌ Patch coverage is 51.06383% with 23 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/EvalFile_Command.php	51.06%	23 Missing ⚠️

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[swissspidy]

Closing in favor of wp-cli/wp-cli#6278