sfxexporter: Add include metrics option

[asuresh4]

Depends on #2145

Description: Add include_metrics option. This option can be used to override the exclusion of metrics. This option can be used to included metrics that are otherwise dropped by default. For example, the following configuration can be used to send through some of that are dropped by default.

include_metrics
  # When sending in translated metrics.
  - metric_names: [cpu.interrupt, cpu.user, cpu.system]
  # When sending in metrics in OTel convention.
  - metric_name: system.cpu.time
    dimensions:
      state: [interrupt, user, system]

Testing: Updated/added tests.

Documentation: Updated README.

[codecov]

Codecov Report

Merging #2146 (3313d86) into master (6bf5f19) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2146      +/-   ##
==========================================
+ Coverage   90.37%   90.38%   +0.01%     
==========================================
  Files         397      397              
  Lines       19498    19509      +11     
==========================================
+ Hits        17621    17634      +13     
+ Misses       1411     1410       -1     
+ Partials      466      465       -1     

Flag	Coverage Δ
integration	69.68% <ø> (ø)
unit	89.17% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
exporter/signalfxexporter/config.go	90.69% <ø> (ø)
exporter/signalfxexporter/exporter.go	97.26% <100.00%> (ø)
exporter/signalfxexporter/translation/converter.go	95.87% <100.00%> (+0.01%)	⬆️
...ignalfxexporter/translation/dpfilters/filterset.go	100.00% <100.00%> (ø)
receiver/k8sclusterreceiver/watcher.go	97.64% <0.00%> (+2.35%)	⬆️

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