feat: relying-party creates SI token for VP query

[paullatzelsperger]

What this PR changes/adds

This PR extends the IdentityAndTrustService and generates another SI token on the relying-party side
which is then used to execute the VP query against the counter-party's CredentialService (= presentation endpoint).

Why it does that

Complete the circle of the presentation flow

Further notes

• Be aware that currently we need to parse the access_token to get the scope string. This is a workaround, until we can extract the scope from the verification context. This behaviour will change in subsequent developments and is only there for the immediate future. The related code has been marked accordingly.
• the access_token constant was renamed to PRESENTATION_ACCESS_TOKEN_CLAIM and is now used everywhere
• this PR also adds the temporary AudienceResolver object, which maps a DSP url to an audience, which can be used to resolve key material

Linked Issue(s)

Closes # <-- insert Issue number if one exists

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[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (1cf48c2) 71.79% compared to head (51023de) 71.81%.

Files	Patch %	Lines
...edc/iam/identitytrust/IdentityAndTrustService.java	87.09%	3 Missing and 1 partial ⚠️
...tytrust/validation/SelfIssuedIdTokenValidator.java	0.00%	1 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3659      +/-   ##
==========================================
+ Coverage   71.79%   71.81%   +0.01%     
==========================================
  Files         917      917              
  Lines       18370    18395      +25     
  Branches     1042     1044       +2     
==========================================
+ Hits        13189    13210      +21     
- Misses       4724     4726       +2     
- Partials      457      459       +2     

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[wolf4ood]

LGTM