[APM] Serverless e2e tests

[kpatticha]

In this PR #160674 we added a basic setup to start running Cypress on serverless environment.

The goal of this ticket is to start adding APM e2e test to cover the following

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1. Left-hand menu - Cypress for observability serverless #160674
2. Feature flags
3. APM onboarding - Cypress tests exists in the current suite, need to move them to serverless suite
4. Happy path (As a user I can ingest traces with synthtrace and see it show up on the service inventory)

As part of this task we need to restructure the folder https://github.com/kpatticha/kibana/tree/395dc32ab4ed1faa0cb043424658b0115e09cb3e/x-pack/test_serverless/functional/test_suites/observability

1. Create a folder landing_page.ts for functional testing
2. https://github.com/kpatticha/kibana/tree/395dc32ab4ed1faa0cb043424658b0115e09cb3e/x-pack/test_serverless/functional/test_suites/observability/cypress/e2e add apm folder and shared

[elasticmachine]

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

[achyutjhunjhunwala]

We also need to update the Testing doc with steps on how to run E2E and API Tests for Serverless

[chrisdistasio]

@smith should we reconsider the overall strategy around testing ui for serverless?

i think we really need to consider both functional and performance ongoing...

[smith]

@chrisdistasio what do you have in mind? @andrewvc has looked at this some, he might have an opinion.

[simitt]

@smith @chrisdistasio @andrewvc could one of you provide a small summary here on where the automated e2e testing stands? I'm interested in educating myself in previous efforts and defining together what should be in place for GA.

[smith]

@simitt The serverless e2e live in https://github.com/elastic/kibana/tree/main/x-pack/test_serverless. The observability tests are there under https://github.com/elastic/kibana/tree/main/x-pack/test_serverless/functional/test_suites/observability.

I think tests in this directory run only for serverless, while the much larger suite of e2e tests is in /x-pack/test.

[simitt]

@smith @kpatticha is this effort done and can this be completed or is there more work left?