[APM] Write browser tests for the APM Create/Edit Integration Settings

[ogupte]

It's important to write and maintain browser tests related to the the APM integration UI since it's a point of integration between Fleet and APM, it should be checked when either plugin has changes. See the existing [Fleet cypress tests] (https://github.com/elastic/kibana/blob/157a37114fba5b1e88c018492e733ed66c29b231/x-pack/test/fleet_cypress/fleet_server.ts) as an example of how to have the Fleet Server set up and enrolled in order to load the policy editor.

Policy Form

when navigating to the integration page
  - [ ] the Elastic APM in Fleet tab is available
  - [ ] the Manage APM integration in Fleet button is available
 
    and clicking on the button
       - [ ] it redirects to the integration policies
       - [ ] if package <= 8.00 tail based is not available
       - [ ] it creates an integration policy 

 when navigating to the integrations policy
   - [ ] it edits the existing integration policy
   - [ ] it deletes the existing integration policy

 when navigating to the integrations policy with installed package >= 8.1.0
   - [ ] it shows tail-based sampling configuration

[elasticmachine]

Pinging @elastic/apm-ui (Team:apm)

[dannycroft]

Possible scenario ideas:

• [APM] Confusing agent onboarding UX after adding the integration #124078
• APM Integration - custom config options not preserved on update #123945
• [Fleet] Fix race condition when editing an upgrade package policy #123762