[Exporter.Geneva] 1.9.0-alpha.1 release prep

[vishweshbankwar]

Fixes #.

Changes

Updates SDK version to 1.9.0-alpha.1 and removes EXPOSE_EXPERIMENTAL_FEATURES directives

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

• Appropriate CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.04%. Comparing base (71655ce) to head (fdbc6a1).
Report is 270 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1834      +/-   ##
==========================================
+ Coverage   73.91%   74.04%   +0.13%     
==========================================
  Files         267      300      +33     
  Lines        9615    11506    +1891     
==========================================
+ Hits         7107     8520    +1413     
- Misses       2508     2986     +478     

Flag	Coverage Δ
unittests-Exporter.OneCollector	89.46% <ø> (?)
unittests-Instrumentation.Http	60.85% <ø> (?)
unittests-Instrumentation.Process	100.00% <ø> (?)
unittests-Instrumentation.Runtime	100.00% <ø> (?)
unittests-Instrumentation.SqlClient	90.90% <ø> (?)
unittests-Instrumentation.StackExchangeRedis	71.00% <ø> (?)
unittests-Instrumentation.Wcf	78.47% <ø> (?)
unittests-Resources.Host	50.00% <ø> (?)
unittests-Solution	80.17% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...eva/Metrics/OtlpProtobuf/OtlpProtobufSerializer.cs	90.65% <ø> (ø)
...metry.Exporter.Geneva/Metrics/TlvMetricExporter.cs	81.30% <ø> (ø)

... and 275 files with indirect coverage changes

[utpilla]

We might not even need this indirection and EXPOSE_EXPERIMENTAL_FEATURES constant anymore. We could consider removing it later.