Self-update in work volumes

[masa213f]

What

When GitHub Runner's self update of is executed, some files are written to the root file system.
It causes the accidentally pod eviction due to the local ephemeral storage limit.

So update on the mounted volume.

actions@dctest-runner-748455d686-nx84c:/$ sudo du -h -d 1 /runner/
131M    /runner/externals.2.283.3 ★
131M    /runner/externals.2.279.0
220M    /runner/_work
80M     /runner/bin.2.283.3 ★
276K    /runner/_diag
80M     /runner/bin.2.279.0
642M    /runner/

How

Describe how to address the issue.

Checklist

• Finish implementation of the issue
• Test all functions
• Have enough logs to trace activities
• Notify developers of necessary actions