Add close method to MetricReader

[jack-berg]

Working #5090 and noticed that MetricReader didn't implement Closeable.

Adjusted MetricReader to extend Closeable, and added a default implementation so the change is backwards compatible. Ran into some issues where japicmp was flagging a false positive that the change was breaking. Ended up needing to dive deeper into the japicmp gradle plugin than I wanted to to discover the source of the bug, but along the way found some better ways to organize our config which make it easier to comprehend.

[codecov]

Codecov Report

Base: 91.06% // Head: 91.06% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (1f3bae9) compared to base (50e7a17).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #5109   +/-   ##
=========================================
  Coverage     91.06%   91.06%           
- Complexity     4885     4886    +1     
=========================================
  Files           553      553           
  Lines         14463    14465    +2     
  Branches       1388     1388           
=========================================
+ Hits          13171    13173    +2     
  Misses          895      895           
  Partials        397      397           

Impacted Files	Coverage Δ
...etry/exporter/prometheus/PrometheusHttpServer.java	80.73% <ø> (ø)
...opentelemetry/sdk/metrics/export/MetricReader.java	100.00% <100.00%> (ø)

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