[Profiling] Annotate TODOs for 9.0.0 upgrade

[danielmitterdorfer]

As suggested by David in #106592, we're adding the annotation @UpdateForV9 to all places in the Universal Profiling plugin that can be removed once we move to 9.0.0.

Relates #106592

[elasticsearchmachine]

Pinging @elastic/obs-knowledge-team (Team:obs-knowledge)

[danielmitterdorfer]

I propose that we:

• move to this approach for tracking 9.0.0 related cleanups (as it's the established practice in the code base and allows to quickly identify the exact places that need to be cleaned up),
• close all issues that are mentioned as subtasks in Universal Profiling cleanups for 9.0.0 #106592.

Up for discussion is whether we keep #106592 open as a placeholder issue or whether we solely rely on the annotation. I'm fine either way.

[rockdaboot]

I propose that we:

* move to this approach for tracking 9.0.0 related cleanups (as it's the established practice in the code base and allows to quickly identify the exact places that need to be cleaned up),

* close all issues that are mentioned as subtasks in [Universal Profiling cleanups for 9.0.0 #106592](https://github.com/elastic/elasticsearch/issues/106592).

Up for discussion is whether we keep #106592 open as a placeholder issue or whether we solely rely on the annotation. I'm fine either way.

I think the annotation alone serves the purpose. We can close the placeholder issue, IMO.

[danielmitterdorfer]

I think the annotation alone serves the purpose. We can close the placeholder issue, IMO.

Cool, that works for me. I'll close all issues then after I've merged the PR. Thanks for the quick response!