Add additional keys from BSL secret to credentials file store

[kaovilai]

Signed-off-by: Tiger Kaovilai tkaovila@redhat.com

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Please add a summary of your change

Add additional files from secret to velero pod without restart to assists with some BSL encryption file requirements without restarting pod. It may require readding BSL to trigger write.

Does your change fix a particular issue?

Fixes #7767

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

Attention: Patch coverage is 52.63158% with 9 lines in your changes missing coverage. Please review.

Project coverage is 59.17%. Comparing base (78c97d9) to head (f3b1d22).

Files with missing lines	Patch %	Lines
internal/credentials/file_store.go	52.63%	6 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7943   +/-   ##
=======================================
  Coverage   59.17%   59.17%           
=======================================
  Files         370      370           
  Lines       39487    39491    +4     
=======================================
+ Hits        23366    23370    +4     
  Misses      14647    14647           
  Partials     1474     1474           

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[kaovilai]

This new key file path follows pattern suggested in #7767 comments.

Below was the original path pattern. Can use prior pattern for just the credentials secret key, or for all keys.
keyFilePath := filepath.Join(n.fsRoot, fmt.Sprintf("%s-%s", selector.Name, selector.Key))