Add proper shutdown implementations for all exporters

[jack-berg]

Add proper shutdown implementation to all the exporters:

• Shutting down multiple times logs a warning
• Calling export after shutdown returns CompletableResultCode.ofFailure() and skips export

[codecov]

Codecov Report

Base: 91.05% // Head: 91.11% // Increases project coverage by +0.05% 🎉

Coverage data is based on head (fa47019) compared to base (b300e72).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5113      +/-   ##
============================================
+ Coverage     91.05%   91.11%   +0.05%     
- Complexity     4886     4914      +28     
============================================
  Files           551      551              
  Lines         14462    14524      +62     
  Branches       1390     1390              
============================================
+ Hits          13169    13233      +64     
+ Misses          894      891       -3     
- Partials        399      400       +1     

Impacted Files	Coverage Δ
...etry/exporter/prometheus/PrometheusHttpServer.java	80.73% <ø> (ø)
...try/exporter/internal/grpc/OkHttpGrpcExporter.java	82.00% <100.00%> (+1.14%)	⬆️
...y/exporter/internal/grpc/UpstreamGrpcExporter.java	91.30% <100.00%> (+1.06%)	⬆️
...metry/exporter/internal/okhttp/OkHttpExporter.java	90.14% <100.00%> (+0.74%)	⬆️
...porter/jaeger/thrift/JaegerThriftSpanExporter.java	81.13% <100.00%> (+7.13%)	⬆️
...logging/otlp/OtlpJsonLoggingLogRecordExporter.java	85.71% <100.00%> (+5.71%)	⬆️
...er/logging/otlp/OtlpJsonLoggingMetricExporter.java	88.46% <100.00%> (+2.74%)	⬆️
...rter/logging/otlp/OtlpJsonLoggingSpanExporter.java	90.90% <100.00%> (+3.40%)	⬆️
...emetry/exporter/logging/LoggingMetricExporter.java	82.75% <100.00%> (+3.59%)	⬆️
...elemetry/exporter/logging/LoggingSpanExporter.java	95.12% <100.00%> (+0.83%)	⬆️
... and 9 more

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