feat: Add diagnostic source integration.

[lucas-zimerman]

See #1150

This PR adds a new project called Sentry.Diagnostics.DiagnosticSource that implements the Diagnostic Source integration, integrating (for now) EF Core and SQLClient.
In addition, the main Sentry project will come with the same integration if the target version is .NET CORE 3.1 or newer.

EF Core

Adds automatic spans for EF Core queries.

It creates spans for measuring the time required to connect to the database, execute the query and optimize it.
If everything went well, the spans will receive the status OK, otherwise, an internal error.

samples
OK Request https://sentry.io/organizations/sentry-sdks/discover/sentry-dotnet:7a363753fbc6446ba983de5006bb5809
On error: https://sentry.io/organizations/sentry-sdks/discover/sentry-dotnet:8806f87262324b45aaf1a9a5fd851f29
Another case of error: https://sentry.io/organizations/sentry-sdks/discover/sentry-dotnet:6424aec6c1684f658144ee29f320f279

SQLClient

Adds automatic spans to any code that interacts with

https://www.nuget.org/packages/Microsoft.Data.SqlClient/
and
https://www.nuget.org/packages/System.Data.SqlClient.

The following Spans are created:

db.connection: measures the connection lifespan.
db.query: measures the time required to execute the query.

[codecov-commenter]

Codecov Report

Merging #1154 (171839e) into main (133e1a5) will decrease coverage by 0.05%.
The diff coverage is 78.39%.

@@            Coverage Diff             @@
##             main    #1154      +/-   ##
==========================================
- Coverage   80.62%   80.57%   -0.06%     
==========================================
  Files         205      212       +7     
  Lines        6647     6846     +199     
  Branches     1508     1563      +55     
==========================================
+ Hits         5359     5516     +157     
- Misses        796      822      +26     
- Partials      492      508      +16     

Impacted Files	Coverage Δ
...sions.Logging/Extensions/KeyValuePairExtensions.cs	0.00% <0.00%> (ø)
src/Sentry/SentryOptionsExtensions.cs	70.76% <50.00%> (-0.66%)	⬇️
...gnosticSource/SentryOptionsDiagnosticExtensions.cs	66.66% <66.66%> (ø)
...als/DiagnosticSource/SentryDiagnosticSubscriber.cs	68.00% <68.00%> (ø)
...osticSource/SentryDiagnosticListenerIntegration.cs	71.42% <71.42%> (ø)
...rce/Internals/Extensions/KeyValuePairExtensions.cs	75.00% <75.00%> (ø)
...ce/Internals/DiagnosticSource/SentrySqlListener.cs	84.09% <84.09%> (ø)
...Internals/DiagnosticSource/SentryEFCoreListener.cs	86.79% <86.79%> (ø)
src/Sentry.AspNet/SentryAspNetOptionsExtensions.cs	100.00% <100.00%> (ø)
.../Sentry.AspNetCore/SentryAspNetCoreOptionsSetup.cs	100.00% <100.00%> (ø)
... and 9 more

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[bruno-garcia]

Quick pass.

[github-actions]

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📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

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