Accessibility tests for APM UI

[smith]

Use cypress-axe to test accessibility in APM UI.

Add the checkA11y() in the e2e for the following pages (for now we are going to set the parameter skipFailures to true, this will log the errors but won't make the test fails, issues to tackle the failures will be created afterwards)

• Services inventory

• Traces

• Dependencies

• Service Map (we don't have e2e test)

• Service overview

• Transactions

• Transaction details

• Errors

• Error details

• Metrics (we don't have e2e)

• Infrastructure

• Logs

Meta issue: elastic/kibana#51456.

[elasticmachine]

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

[elasticmachine]

Pinging @elastic/kibana-accessibility (Project:Accessibility)

[elasticmachine]

Pinging @elastic/obs-ux-infra_services-team (Team:obs-ux-infra_services)