## Summary

This PR update Scout discovery command to optionally include configs
associated with custom servers directories (located under
`test/scout_*/` path):

```bash
node scripts/scout.js discover-playwright-configs --include-custom-servers
```

Since some Teams may decide not to run their config in the unified Scout
CI execution, I added `excluded_configs` in
`.buildkite/scout_ci_config.yml` to list them explicitly:

```
plugins:
  enabled:
    - apm
    - console
    ...
  disabled:

packages:
    ...

# Define test configs to be excluded from automatic discovery & execution in CI environment (process.env.CI=true)
excluded_configs:
  - x-pack/solutions/security/plugins/cloud_security_posture/test/scout_cspm_agentless/ui/parallel.playwright.config.ts
```

While running on CI environment `node scripts/scout.js
discover-playwright-configs` will exclude those configs and they won't
be run.

This PR also removed uiam tests custom CI script/step definition as it
is no longer needed.

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
(cherry picked from commit 7b13120)

# Conflicts:
#	.buildkite/pipelines/es_serverless/verify_es_serverless_image.yml
#	.buildkite/pipelines/on_merge.yml
#	.buildkite/pipelines/pull_request/profiling_cypress.yml
#	.buildkite/scout_ci_config.yml
#	.buildkite/scripts/pipelines/pull_request/pipeline.ts
#	.buildkite/scripts/steps/test/scout_test_run_builder.sh
#	src/platform/packages/shared/kbn-scout/src/cli/config_discovery.test.ts

…rectory