[FEATURE] Handle deprecations better

[kavilla]

Origin: #1600 (comment)

Summary

Some methods within Painless Scripting were deprecated since the time of the fork. However, the warning message about the deprecation were only added to the log files. For 3.0, these deprecated methods will be removed to which point if the methods were not updated within the scripted fields then application will appear broken without a clear reason why. For the most part, we can assume if scripted fields were working fine then end users were not checking the logs to see the deprecated warning, and since this is a breaking change from OpenSearch, it will not be in our release notes. There might be risk of users not realizing this breaking change and then not know what to do.

Proposal

Some in application way to inform users of future deprecation/removed content to prevent potential impact to productivity.