[meta]: improving developer experience in testing and ci

[efd6]

This is a collection of mainly elastic-package issues that relate to DX in local and CI elastic-package use in testing.

• Availability of serverless-version stacks for local testing
  • [Serverless] Support testing against development serverless projects #1808
• Ability to inject debugging agents into running test stacks
  • Allow users to specify a download source for beats packages #1319
• Reporting exact stack versions in tests (currently e.g. “serverless (security)” is a reported version, which is not useful)
  • Exact build version is not emitted for some builds integrations#13553
• Quality of failure logging in CI (signal/noise ratio, informative output discoverability)
  • verbosity of logging: Re-assess output shown in elastic-package when running tests in CI #1903
  • info quality of field checks: feature: improve error messages for package field validation checks #994
  • version discoverability: feature: render package, stack and elastic-package version into test reports #991
• Testing
  • Multiple service deployers: Support deploying multiple services in system tests #1302
  • Unhappy path: proposal: provide mechanism to test unhappy path behaviour #1941
  • kibana.version constraint: elastic-package test should respect package kibana version constraints #873