Remove unnecessary calls and errors in patterns

[joshuali925]

Description

• Remove PPL call to get doc_count for patterns ratio, use in memory data instead (prometheus does not support stats count() without by
• Remove errors from AD call in toasts, UI will show N/A for anomalies column if ml-commons plugin is not installed or responding error

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[codecov-commenter]

Codecov Report

Merging #1243 (4445834) into 2.4 (0224c23) will decrease coverage by 0.06%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##                2.4    #1243      +/-   ##
============================================
- Coverage     54.66%   54.59%   -0.07%     
  Complexity      292      292              
============================================
  Files           283      283              
  Lines          9787     9797      +10     
  Branches       2295     2299       +4     
============================================
- Hits           5350     5349       -1     
- Misses         4266     4277      +11     
  Partials        171      171              

Flag	Coverage Δ
dashboards-observability	49.50% <0.00%> (-0.09%)	⬇️
opensearch-observability	70.35% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...hboards-observability/common/constants/explorer.ts	100.00% <ø> (ø)
...mponents/event_analytics/hooks/use_fetch_events.ts	1.38% <0.00%> (-0.04%)	⬇️
...onents/event_analytics/hooks/use_fetch_patterns.ts	1.44% <0.00%> (-0.17%)	⬇️
...ards-observability/public/services/requests/ppl.ts	55.55% <0.00%> (-6.95%)	⬇️
.../public/components/custom_panels/helpers/utils.tsx	72.86% <0.00%> (-0.37%)	⬇️

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