chore: Add Open-API spec for missing endpoints

[bstasyszyn]

Added Open-API for loglevels and sidetree endpoints.

Also refactored the /loglevels endpoint to move it to its own package.

[codecov]

Codecov Report

Patch coverage: 85.71% and project coverage change: -0.02 ⚠️

Comparison is base (f716271) 88.04% compared to head (9ae181a) 88.02%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1535      +/-   ##
==========================================
- Coverage   88.04%   88.02%   -0.02%     
==========================================
  Files         219      223       +4     
  Lines       20764    20768       +4     
==========================================
  Hits        18282    18282              
- Misses       1584     1588       +4     
  Partials      898      898              

Impacted Files	Coverage Δ
cmd/orb-server/startcmd/log.go	100.00% <ø> (+6.12%)	⬆️
pkg/document/resolvehandler/openapi.go	0.00% <0.00%> (ø)
pkg/document/updatehandler/openapi.go	0.00% <0.00%> (ø)
pkg/observability/loglevels/openapi.go	0.00% <0.00%> (ø)
pkg/observability/loglevels/loglevels.go	93.02% <93.02%> (ø)
cmd/orb-server/startcmd/start.go	66.97% <100.00%> (ø)

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