Deprecate HotChocolate.Templates.Server

[glen-84]

Summary of the changes (Less than 80 chars)

• Deleted templates/Server directory.
• Updated build configuration.
• Updated v12 & v13 docs.

Closes #5846

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@michaelstaib Can you deprecate the package on NuGet?

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (584b932) 70.89% compared to head (10d7c79) 73.69%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
...tCore/Extensions/EndpointRouteBuilderExtensions.cs	88.88%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6834      +/-   ##
==========================================
+ Coverage   70.89%   73.69%   +2.80%     
==========================================
  Files        2520     2534      +14     
  Lines      126678   127322     +644     
==========================================
+ Hits        89805    93836    +4031     
+ Misses      36873    33486    -3387     

Flag	Coverage Δ
unittests	73.69% <88.88%> (+2.80%)	⬆️

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