feat: make pub/priv aliases mandatory at startup

[ndr-brt]

What this PR changes/adds

Read priv/pub aliases from configuration at startup, ensuring that the runtime won't start if they're not provided.

Why it does that

Avoid lazy failures.

Further notes

• Fixed some test tags (that will distribute tests in different ci jobs in a better way)
• in the transfer e2e created the noPolicyConstraints just once.
• EDIT: I took the opportunity to get rid of the infamous backend-service, relying only on instances of mockserver instead

Linked Issue(s)

Closes #3994

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 75.18%. Comparing base (7f20ba5) to head (2b88a6f).
Report is 327 commits behind head on main.

Files	Patch %	Lines
...ramework/DataPlaneDefaultIamServicesExtension.java	0.00%	10 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4304      +/-   ##
==========================================
+ Coverage   71.74%   75.18%   +3.43%     
==========================================
  Files         919     1052     +133     
  Lines       18457    21114    +2657     
  Branches     1037     1180     +143     
==========================================
+ Hits        13242    15874    +2632     
+ Misses       4756     4725      -31     
- Partials      459      515      +56     

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[jimmarino]

• EDIT: I took the opportunity to get rid of the infamous backend-service, relying only on instances of mockserver instead

😄 🪓