Expose response ContentTypes in api-definition and use them in proxies

[maliming]

Expose response ContentTypes and IsRemoteStream flag in api-definition so C# / jQuery / Angular proxies can echo back the actual declared media type instead of collapsing everything to application/json + text/plain. Also unwraps ABP error envelopes in RestService for text and blob response modes. The jQuery generator and Angular schematic now forward DTO uploads containing IRemoteStreamContent as multipart FormData instead of JSON.

Closes #23732
Closes #8581

[codecov]

Codecov Report

❌ Patch coverage is 90.07634% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.38%. Comparing base (59e2a99) to head (025e495).
⚠️ Report is 16 commits behind head on dev.

Files with missing lines	Patch %	Lines
.../Abp/Http/Client/ClientProxying/ClientProxyBase.cs	86.44%	5 Missing and 3 partials ⚠️
...ng/Generators/JQuery/JQueryProxyScriptGenerator.cs	87.50%	2 Missing and 2 partials ⚠️
...tCore/Mvc/AspNetCoreApiDescriptionModelProvider.cs	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #25639      +/-   ##
==========================================
+ Coverage   49.36%   49.38%   +0.02%     
==========================================
  Files        3687     3687              
  Lines      124432   124537     +105     
  Branches     9507     9532      +25     
==========================================
+ Hits        61421    61500      +79     
- Misses      61171    61210      +39     
+ Partials     1840     1827      -13     

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