[Tests] Simplify usage of SamplingResult constructor

[Kielek]

Changes

Cleanup code after 1.9.0 release. Ref: open-telemetry/opentelemetry-dotnet#5614
Minor other cleanups while checking all usages of the constructor.

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 79.97%. Comparing base (71655ce) to head (2d671df).
Report is 335 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1915      +/-   ##
==========================================
+ Coverage   73.91%   79.97%   +6.05%     
==========================================
  Files         267       29     -238     
  Lines        9615      824    -8791     
==========================================
- Hits         7107      659    -6448     
+ Misses       2508      165    -2343     

Flag	Coverage Δ
unittests-Instrumentation.AspNet	74.85% <ø> (?)
unittests-Instrumentation.AspNetCore	85.27% <ø> (?)
unittests-Instrumentation.ElasticsearchClient	79.87% <ø> (?)

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see 280 files with indirect coverage changes