[AzureMonitor] Change drop sampling result to recordOnly

[vishweshbankwar]

Fixes #.

Changes

Sampler will now return RecordOnly SamplingResult when the telemetry is sampled instead of Drop. This will result activity object to be created always and populated with all information such as tag, events etc. This is done in order to allow standard
metrics collection from the generated activities.

The change is needed in order to provide feature parity to current Application Insights SDK customers moving to OpenTelemetry.

Note: This change will have no impact on the overall sampling behavior.

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #

[codecov]

Codecov Report

Merging #933 (f614f34) into main (cad8d76) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head f614f34 differs from pull request most recent head 94bde42. Consider uploading reports for the commit 94bde42 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #933      +/-   ##
==========================================
- Coverage   68.38%   68.38%   -0.01%     
==========================================
  Files         183      183              
  Lines        7026     7025       -1     
==========================================
- Hits         4805     4804       -1     
  Misses       2221     2221              

Impacted Files	Coverage Δ
...ensions.AzureMonitor/ApplicationInsightsSampler.cs	96.55% <100.00%> (ø)
...entation.AspNet/TracerProviderBuilderExtensions.cs	100.00% <0.00%> (ø)

[Kielek]

Changes looks good, but it will be great to include some explanation why it is needed (maybe first comment in the PR?).

[CodeBlanch]

@Kielek I was curious too so I chatted with @vishweshbankwar about this. This sampling behavior matches what AppInsights does today so it is about bringing parity for those customers moving to OTel.