Add user documentation for Compiler Extensions

[Flash0ver]

Description

We currently have two compiler extensions:

• a Source Generator: see https://github.com/getsentry/sentry-dotnet/blob/main/src/Sentry.Compiler.Extensions/BuildPropertySourceGenerator.cs
• a Diagnostic Analyzer: feat(metrics): Trace-connected Metrics (Analyzers) #4840

Let's add some documentation with a brief description, example, and when/how to disable / suppress these.

• Functionality and Intent of the Source Generator
  • document how to disable it in case of issues
  • see

    sentry-dotnet/src/Sentry.Compiler.Extensions/BuildPropertySourceGenerator.cs

    Line 34 in 50186be

    if (opts.TryGetValue("build_property.SentryDisableSourceGenerator", out var disable) &&

• Functionality and Intent of the Analyzer
  • document how to suppress this Diagnostic (ID: SENTRY1001)
  • document how to suppress all Sentry Diagnostics (Category: Sentry)
  • see also feat(metrics): Trace-connected Metrics (Analyzers) #4840 (comment)

[linear]

NET-598