Fix bug in paginating multiple bucket paths for Bucket-Level Monitor

[qreshi]

Signed-off-by: Mohammad Qureshi qreshi@amazon.com

Issue #, if available: #86

Description of changes:
For Bucket-Level Monitors, different Triggers can potentially have different bucket paths that they are evaluating the conditions against. For paginated aggregation queries, different bucket paths could have different page counts meaning that they will completed independently as the data is being paginated. This change makes it so the after_key can be independently kept for each bucket path to handle the case where one bucket path completes pagination while the others still have data to be iterated through.

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[codecov-commenter]

Codecov Report

Merging #163 (e8e3632) into main (cc0fb6f) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main     #163   +/-   ##
=========================================
  Coverage     78.70%   78.71%           
+ Complexity      215      214    -1     
=========================================
  Files           172      172           
  Lines          6937     6947   +10     
  Branches        901      906    +5     
=========================================
+ Hits           5460     5468    +8     
- Misses          989      992    +3     
+ Partials        488      487    -1     

Impacted Files	Coverage Δ
...ain/kotlin/org/opensearch/alerting/InputService.kt	88.52% <100.00%> (+0.59%)	⬆️
.../org/opensearch/alerting/model/MonitorRunResult.kt	82.82% <100.00%> (+0.17%)	⬆️
...ensearch/alerting/util/AggregationQueryRewriter.kt	73.68% <100.00%> (+4.93%)	⬆️
...ing/destination/client/DestinationEmailClient.java	72.50% <0.00%> (-5.00%)	⬇️
...ing/model/destination/DestinationContextFactory.kt	66.66% <0.00%> (ø)

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