Update LangVersion. Consolidate styling and conventions.

[fiseni]

Closes #342, Closes #343. This was a tedious job, but it had to be done.

• Updated C# version to 11.
• Consolidated project files (.csproj)
• Consolidated test project files and updated report generation.
• Updated pipelines - use NET 7 SDK (we need it for C#11), fix docker files, etc.
• Updated .editorconfig and applied the styling.
• Manually updated all inconsistencies (the usage of this and all other details).
• Added config to ignore some warnings related to missing XML comments (it was polluting the output, and we were missing more important stuff). Ignored the following warning:
  • 1591 Missing XML comment for publicly visible type or member 'Type_or_Member'
  • 1573 Parameter 'parameter' has no matching param tag in the XML comment for 'parameter'
  • 1712 Type parameter 'type parameter' has no matching typeparam tag in the XML comment on 'type'
• Other fixes and cleanup.

Note: @ardalis the 2-space indent is making the code hard to read (e.g. check this file). I do understand that you like that style, but if you change your mind let me know :)

[fiseni]

Hide whitespaces while reviewing, otherwise it's overwhelming.

[ardalis]

This was... big. :)