[sumologicexporter] Add prometheus formatter for metrics

[sumo-drosiek]

Description:
Add prometheus formatter for metrics.

NOTE: metricPair is a structure which will hold information about metrics attributes and metrics itself.
This structure is required to handle all information we want to export to sumologic

Link to tracking Issue: #1498

Testing:

• Unit tests
• Visual comparison tests with prometheus exporter

Documentation:
In-code comments

[sumo-drosiek]

cc: @pmalek-sumo @pmm-sumo

[codecov]

Codecov Report

Merging #1890 (595f510) into master (fe1b43a) will increase coverage by 0.19%.
The diff coverage is 99.52%.

@@            Coverage Diff             @@
##           master    #1890      +/-   ##
==========================================
+ Coverage   89.90%   90.10%   +0.19%     
==========================================
  Files         380      382       +2     
  Lines       18335    18756     +421     
==========================================
+ Hits        16484    16900     +416     
- Misses       1385     1388       +3     
- Partials      466      468       +2     

Flag	Coverage Δ
integration	69.82% <ø> (ø)
unit	88.84% <99.52%> (+0.22%)	⬆️

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Impacted Files	Coverage Δ
exporter/sumologicexporter/sender.go	91.45% <ø> (ø)
exporter/sumologicexporter/prometheus_formatter.go	99.20% <99.20%> (ø)
exporter/sumologicexporter/test_data.go	100.00% <100.00%> (ø)
receiver/k8sclusterreceiver/watcher.go	95.29% <0.00%> (-2.36%)	⬇️
processor/groupbytraceprocessor/event.go	95.96% <0.00%> (-0.81%)	⬇️

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