Add Sentry to global usings

[SimonCropp]

fixes #1163

• Add docs about opting in to implicit usings and how to resolve conflicts. consider add a pointer to feature here https://docs.sentry.io/platforms/dotnet/ add Implicit Usings docs sentry-docs#4585

[lucas-zimerman]

Is it possible to add some tests for it?

[bruno-garcia]

❤️

Do we need a major bump here and docs to help users opt-out if they have conflicts?

More importantly: Isn't this going to immediately break anyone using Span<T>?

[codecov-commenter]

Codecov Report

Merging #1398 (76e2c80) into main (4f304c1) will decrease coverage by 1.37%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1398      +/-   ##
==========================================
- Coverage   84.16%   82.79%   -1.38%     
==========================================
  Files         219      219              
  Lines        7346     7346              
  Branches     1409     1409              
==========================================
- Hits         6183     6082     -101     
- Misses        729      838     +109     
+ Partials      434      426       -8     

Impacted Files	Coverage Δ
src/Sentry/PlatformAbstractions/FrameworkInfo.cs	0.00% <0.00%> (-100.00%)	⬇️
...ntry/PlatformAbstractions/RegistryKeyExtensions.cs	0.00% <0.00%> (-100.00%)	⬇️
...Sentry/PlatformAbstractions/FrameworkInfo.NetFx.cs	0.00% <0.00%> (-70.43%)	⬇️
...rmAbstractions/NetFxInstallationsEventProcessor.cs	4.54% <0.00%> (-68.19%)	⬇️
...ntry/PlatformAbstractions/FrameworkInstallation.cs	25.00% <0.00%> (-37.50%)	⬇️
...ntry/Integrations/NetFxInstallationsIntegration.cs	28.57% <0.00%> (-28.58%)	⬇️
src/Sentry/PlatformAbstractions/RuntimeInfo.cs	53.44% <0.00%> (-5.18%)	⬇️
src/Sentry/Internal/BackgroundWorker.cs	92.02% <0.00%> (-1.45%)	⬇️
src/Sentry/Internal/AppDomainAdapter.cs	66.66% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4f304c1...76e2c80. Read the comment docs.

[bruno-garcia]

@SimonCropp feel free to merge this once we have some docs to go with it.
I also propose causing a conflict on purpose to get an error message and throw it in the Troubleshooting page: https://docs.sentry.io/platforms/dotnet/troubleshooting/ There we can point out how users can't opt-out of this or how to resolve the conflict. If that would be beneficial.