Remove integtest.sh from all plugin repos

[setiah]

The integtest.sh tool contains the logic to run integration tests for a plugin. This logic is mostly common across most plugins, so it has been moved to opensearch-build repo. Thus it can be removed from the individual plugin repos.
However, if a plugin requires some custom logic to run integtests, which the standard tool doesn't provide, they can continue maintaining this integtest.sh in their own repo. In this case, when the integration tests are run, if a plugin has a integtest.sh tool in their repo, it gets precedence over the standard default integtest.sh in the opensearch-build repo. This precedence order logic is defined in ScriptFinder here

Action items:

Raise PRs on all plugin repos and remove integtest.sh

• index-management
• anomaly-detection,
• alerting
• asynchronous-search
• k-NN

Changes will need to be backported into 1.x branches if such exist, too.

[dblock]

I took the liberty to make PRs in all plugin repos that had an integtest.sh file using meta, see opensearch-project/opensearch-plugins#80.

[dblock]

• Remove integtest sh (1.1) anomaly-detection#220
• Removed default integtest.sh (1.1). sql#213
• Remove integtest sh 1.1 alerting#181
• Remove integhtest sh from 1.1 k-NN#101