Add Title to Diagnostics

[erri120]

As discussed in a meeting last week, this adds a Title property to Diagnostic.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 54.54545% with 10 lines in your changes are missing coverage. Please review.

Project coverage is 55.05%. Comparing base (c499846) to head (9975ac1).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1073      +/-   ##
==========================================
+ Coverage   54.84%   55.05%   +0.20%     
==========================================
  Files         662      660       -2     
  Lines       22022    21954      -68     
  Branches     1710     1702       -8     
==========================================
+ Hits        12079    12087       +8     
+ Misses       9549     9469      -80     
- Partials      394      398       +4     

Flag	Coverage Δ
Linux	54.36% <54.54%> (+0.19%)	⬆️
Windows	54.24% <54.54%> (+0.16%)	⬆️
clean_environment_tests	55.04% <54.54%> (+0.21%)	⬆️
macOS	53.80% <54.54%> (+0.17%)	⬆️
network_tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...sMods.Abstractions.Games.Diagnostics/Diagnostic.cs	70.00% <100.00%> (+3.33%)	⬆️
...ons.Games.Diagnostics/DiagnosticTemplateBuilder.cs	0.00% <ø> (ø)
...ountAndBlade2Bannerlord/Emitters/BuiltInEmitter.cs	58.22% <100.00%> (+0.53%)	⬆️
...Tests/Diagnostics/DummyLoadoutDiagnosticEmitter.cs	0.00% <0.00%> (ø)
...del.Tests/Diagnostics/DummyModDiagnosticEmitter.cs	0.00% <0.00%> (ø)
...cs/DiagnosticTemplateIncrementalSourceGenerator.cs	81.17% <83.33%> (+0.02%)	⬆️
...aModel.Tests/Diagnostics/DiagnosticManagerTests.cs	0.00% <0.00%> (ø)
...Games/NexusMods.Games.StardewValley/Diagnostics.cs	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes