* Adds a shared note that the migration APIs are mainly intended for internal use by Kibana's Upgrade Assistant.
* Updates the feature migration API docs to use updated "migration" terminology.
* Removes some references to major versions from the deprecation API docs.
Removes `testenv` annotations and related code. These annotations originally let you skip x-pack snippet tests in the docs. However, that's no longer possible.
Relates to #79309, #31619
This commit adds the ability to configure a list of settings that will be ignored by the deprecation info
API. Any deprecation messages for any of the settings given will be suppressed. This can be used to hide
settings that users do not have the ability to change.
Relates #78725
This commit gets rid of the 'NONE' and 'INFO' severity levels for
deprecation issues.
'NONE' is unused and does not make much sense as a severity level.
'INFO' can be separated into two categories: Either 1) we can
definitively tell there will be a problem with the cluster/node/index
configuration that can be resolved prior to upgrade, in which case
the issue should be a WARNING, or 2) we can't, because any issues would
be at the application level, for which the user should review the
deprecation logs and/or response headers.
