Feat: Enhance GCP Integraction.

[lucas-zimerman]

This PR brings two new sets of features:

• Performance monitoring for Google Cloud Functions.
• Correct setup of Release version with the GCP revision number.

In addition, the GCP sample got the Tracing Sample rate to 1.0.

NOTE: Both Transaction names and revision numbers will only be set on Google's environment and not locally.

[lucas-zimerman]

@SimonCropp This PR will have some changes into public fields, what's the best approach for updating the public fields check?

[codecov-commenter]

Codecov Report

Merging #1286 (62df16d) into main (aa6a149) will increase coverage by 0.14%.
The diff coverage is 96.66%.

@@            Coverage Diff             @@
##             main    #1286      +/-   ##
==========================================
+ Coverage   81.69%   81.84%   +0.14%     
==========================================
  Files         212      212              
  Lines        7047     7076      +29     
  Branches     1393     1397       +4     
==========================================
+ Hits         5757     5791      +34     
+ Misses        848      845       -3     
+ Partials      442      440       -2     

Impacted Files	Coverage Δ
src/Sentry.Google.Cloud.Functions/SentryStartup.cs	98.14% <96.15%> (-1.86%)	⬇️
...try.AspNetCore/Extensions/HttpContextExtensions.cs	83.33% <100.00%> (+1.11%)	⬆️
src/Sentry/Internal/Hub.cs	73.54% <0.00%> (+1.05%)	⬆️
src/Sentry/SentrySdk.cs	81.96% <0.00%> (+1.63%)	⬆️
src/Sentry.AspNetCore/SentryTracingMiddleware.cs	76.82% <0.00%> (+2.43%)	⬆️
src/Sentry/Extensibility/HubAdapter.cs	72.72% <0.00%> (+3.03%)	⬆️

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