Fix/sampler shutdown lifecycle

[Debashismitra01]

Changes

Adds shutdown lifecycle support to Samplers.

Previously Sampler implementations had no way to release resources when
SdkTracerProvider was shut down. Resource-owning samplers such as
JaegerRemoteSampler could leave background executors and connections running.

This change:

• Adds default Sampler.shutdown()
• Invokes sampler shutdown from SdkTracerProvider shutdown
• Updates JaegerRemoteSampler to release polling and sender resources
• Adds lifecycle tests

Fixes #8535

[otelbot]

⚠️ API changes detected — additional maintainer review required

@jack-berg @jkwatson

This PR modifies the public API surface area of the following module(s):

• opentelemetry-sdk-extension-jaeger-remote-sampler
• opentelemetry-sdk-trace

Please review the changes in docs/apidiffs/current_vs_latest/ carefully before approving.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.56%. Comparing base (2626179) to head (f246d3e).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8574      +/-   ##
============================================
+ Coverage     90.96%   91.56%   +0.59%     
- Complexity    10207    10266      +59     
============================================
  Files          1013     1013              
  Lines         27160    27115      -45     
  Branches       3182     3184       +2     
============================================
+ Hits          24706    24827     +121     
+ Misses         1730     1564     -166     
  Partials        724      724              

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[jkwatson]

Thanks! I'll let @jack-berg also approve before merging, as there's an API change.