Replace uses of os.Create with os2.Create within backup/restore workflows

[mattrobenolt]

This abstracts this ever so slightly into a new os2.Create to replace usages of os.Create across packages.

I didn't want to address every single use of os.Create within this PR, but ideally we'd review other uses and swap them to use this version.

This prevents files from being created and written with world read/write privileges. I strongly don't think any of these cases, that behavior was intentional, rather implicit due to using os.Create which internally uses 0666 permissions.

Note

I think that this should be backported to all supported releases (back to v19 today) since it improves the product's security posture.

Related Issue(s)

Fixes #17647

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

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[codecov]

Codecov Report

Attention: Patch coverage is 65.00000% with 7 lines in your changes missing coverage. Please review.

Project coverage is 67.75%. Comparing base (9c6c380) to head (ad753a6).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/mysqlctl/mysqld.go	0.00%	5 Missing ⚠️
go/os2/file.go	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17648      +/-   ##
==========================================
- Coverage   67.76%   67.75%   -0.01%     
==========================================
  Files        1586     1587       +1     
  Lines      255763   255772       +9     
==========================================
- Hits       173315   173310       -5     
- Misses      82448    82462      +14     

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[mattlord]

Thanks, @mattrobenolt ! ❤️