[mongodb] Add MongoDB Plugin

[timkante]

• I adjusted the corresponding documentation for this change.
• I adjusted the values.yaml file and the documentation for all values.

[codecov-commenter]

Codecov Report

Merging #431 (2e097ef) into main (f810912) will decrease coverage by 0.97%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #431      +/-   ##
==========================================
- Coverage   45.45%   44.47%   -0.98%     
==========================================
  Files         139      141       +2     
  Lines       11938    12199     +261     
==========================================
  Hits         5426     5426              
- Misses       6373     6634     +261     
  Partials      139      139              

Impacted Files	Coverage Δ
cmd/kobs/main.go	0.00% <0.00%> (ø)
plugins/plugin-jaeger/cmd/jaeger.go	18.40% <0.00%> (-0.12%)	⬇️
plugins/plugin-jaeger/pkg/instance/instance.go	18.51% <0.00%> (-0.97%)	⬇️
plugins/plugin-mongodb/cmd/mongodb.go	0.00% <0.00%> (ø)
plugins/plugin-mongodb/pkg/instance/instance.go	0.00% <0.00%> (ø)

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