Add functionality to support patterns in --user flag

[verbanicm]

Fixes: #5827

Description

• Added pattern matching for --user flag
• Accepted patterns: ^allowedUser(\/.+)?$ IE: string or string/string
• Valid Examples: vsc or vsc/staging
• Invalid Examples: vsc/ vsc|development random-string

[codecov]

Codecov Report

Merging #6402 (229c264) into main (10f4672) will increase coverage by 0.01%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##             main    #6402      +/-   ##
==========================================
+ Coverage   70.36%   70.38%   +0.01%     
==========================================
  Files         499      500       +1     
  Lines       22725    22733       +8     
==========================================
+ Hits        15991    16000       +9     
+ Misses       5691     5689       -2     
- Partials     1043     1044       +1     

Impacted Files	Coverage Δ
pkg/skaffold/user/user.go	75.00% <75.00%> (ø)
pkg/skaffold/instrumentation/export.go	64.00% <100.00%> (ø)
pkg/skaffold/version/version.go	100.00% <100.00%> (ø)
pkg/skaffold/log/stream/stream.go	81.25% <0.00%> (+18.75%)	⬆️

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