[PROPOSAL] Add a checkbox in each plugin's PR templates to update API specs

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What/Why

What are you proposing?

The same as opensearch-project/OpenSearch#13621 in each plugin.

What users have asked for this feature?

All users of OpenSearch that use language clients.

What problems are you trying to solve?

From opensearch-project/OpenSearch#13619

With the introduction of OpenSearch API Specification for generating client libraries and documentation in multiple languages, it is possible that new features might miss out on defining the APIs, leading in gaps in what the generated clients for exotic languages can support.

What is the developer experience going to be?

Create companion PRs for every API change with an OpenAPI spec and a test.

Dependent PRs

• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. common-utils#696
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. alerting#1596
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. anomaly-detection#1262
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. asynchronous-search#591
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. cross-cluster-replication#1407
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. custom-codecs#162
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. flow-framework#773
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. geospatial#666
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. index-management#1202
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. job-scheduler#649
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. k-NN#1801
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. ml-commons#2620
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. neural-search#823
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. notifications#932
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. observability#1841
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. opensearch-oci-object-storage#61
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. reporting#1012
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. performance-analyzer#679
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. security-analytics#1150
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. security#4533
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. skills#346
• Update PULL_REQUEST_TEMPLATE to include an API spec change in the checklist. sql#2808

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This is done! cc: @vamshin