docs: changelogs and compatibility matrix to reflect a bugfix that can lead to missing metrics

[simitt]

elastic/apm-data#157 fixed a bug in the apm-server where a validation was not properly applied. Before the fix, empty metricset values were accepted by the apm-server, although they should have been rejected. The fix was released in 8.11.0.
The apm-java-agent had been sending empty histogram metricsets for micrometer up until version 1.42, and fixed the bug on the agent side in 1.43.0.

The fixes impact users of the java agent in a version <1.43.0, where empty micrometer histogram metrics would be recorded. The docs need to be updated accordingly for visibility before upgrading the server.

1. 8.11 release notes should contain a note that the validation was fixed, requiring users to upgrade to java agent version >= 1.43.0 if they are collecting micrometer or custom metrics with potentially empty .
2. Update the https://www.elastic.co/guide/en/apm/guide/8.11/known-issues.html section with a note
3. Update the https://www.elastic.co/guide/en/apm/guide/current/agent-server-compatibility.html compatibility matrix with a * annotation explaining the edge case where the agent is not compatible with the server

[simitt]

@colleenmcginnis @bmorelli25 would you be able to help us out with these docs and where they need to be updated atm?

[colleenmcginnis]

@simitt there's a draft PR up here: elastic/observability-docs#3591. Can you take a look?