* feat(config): add experimental exitCodeForErrors option
* feat(config): give unknown-error its own exit code
* docs: restore exit codes 1 and 2 to the table
* refactor(onboarding): return repository result from ensureOnboarding
Rename ensureOnboardingPr to ensureOnboarding and have it return a new
'onboarding' RepositoryResult. renovateRepository now branches on
repoIsOnboarded, so exactly one of ensureOnboarding/updateRepo produces
the repository result and the non-null assertion on the update result
(TODO #22198) is no longer needed. updateRepo/update no longer return
undefined for non-onboarded repositories.
* refactor(onboarding): keep ensureOnboardingPr name
RahulGautamSingh