feat: add catalog endpoints schema examples

[ndr-brt]

What this PR changes/adds

Openapi spec examples for catalog api

Why it does that

documentation

Further notes

• add also missing Policy example
• removed the no-more-useful openapi.yaml

Linked Issue(s)

Closes #3115
Closes #3146
Part of #3267

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[codecov-commenter]

Codecov Report

Patch coverage: 66.66% and project coverage change: -0.08 ⚠️

Comparison is base (112ade7) 71.63% compared to head (9d42d65) 71.55%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3306      +/-   ##
==========================================
- Coverage   71.63%   71.55%   -0.08%     
==========================================
  Files         831      830       -1     
  Lines       16681    16659      -22     
  Branches      953      953              
==========================================
- Hits        11949    11920      -29     
- Misses       4336     4341       +5     
- Partials      396      398       +2     

Impacted Files	Coverage Δ
.../eclipse/edc/validator/jsonobject/JsonWalkers.java	76.92% <0.00%> (-7.70%)	⬇️
.../java/org/eclipse/edc/api/model/ApiCoreSchema.java	0.00% <ø> (ø)
.../management/configuration/ManagementApiSchema.java	0.00% <0.00%> (ø)
...c/connector/api/management/catalog/CatalogApi.java	0.00% <0.00%> (ø)
...nt/contractnegotiation/ContractNegotiationApi.java	0.00% <ø> (ø)
...tor/api/management/policy/PolicyDefinitionApi.java	0.00% <ø> (ø)
...ansform/JsonObjectToCatalogRequestTransformer.java	77.77% <77.77%> (ø)
...r/api/management/catalog/CatalogApiController.java	89.47% <100.00%> (-0.53%)	⬇️
...or/api/management/catalog/CatalogApiExtension.java	83.33% <100.00%> (-2.39%)	⬇️
...nt/catalog/validation/CatalogRequestValidator.java	83.33% <100.00%> (ø)

... and 1 file with indirect coverage changes

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