feat: add findById method on DataPlaneSelectorService

[ndr-brt]

What this PR changes/adds

Add findById method on DataPlaneSelectorService

Why it does that

Avoid unnecessary calls to getAll

Further notes

List other areas of code that have changed but are not necessarily linked to the main feature. This could be method
signature changes, package declarations, bugs that were encountered and were fixed inline, etc.

Linked Issue(s)

Closes #4210

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 91.30435% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 75.36%. Comparing base (7f20ba5) to head (f9730db).
Report is 283 commits behind head on main.

Files	Patch %	Lines
...plane/selector/RemoteDataPlaneSelectorService.java	84.61%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4225      +/-   ##
==========================================
+ Coverage   71.74%   75.36%   +3.62%     
==========================================
  Files         919     1039     +120     
  Lines       18457    20640    +2183     
  Branches     1037     1152     +115     
==========================================
+ Hits        13242    15556    +2314     
+ Misses       4756     4573     -183     
- Partials      459      511      +52     

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[wolf4ood]

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