[Uptime] Add feedback link to Kibana help menu item as custom content

[formgeist]

Summary

Kibana are adding a global help menu item to the global header, and in this each app is able to add custom content and link to i.e. the Discuss forum for feedback (see example in issue referenced).

The PR #29664 has a summary of how to get it added in each app.

APM example

Tasks

• Remove the existing "Feedback" option in the local navigation (legacy from 6.x)
• Add link to the respective discuss forums for solutions - label i.e.: Provide feedback for APM

[elasticmachine]

Pinging @elastic/uptime

[shahzad31]

this has been fixed, and some of the remaining refactoring is done in #38542