Implement `failure_reason` on `ci_builds`

Description

Here is the @ayufan's comment on ci_builds.failure_reason

RegisterJobService, if cannot be picked it should fail. We probably need to introduce ci_builds.failure_reason. And use that failure_reason in Detailed Build Status.

I see the following failure_reasons:

• script_error,

• system_error,

• missing_dependency,

• out_of_quota,

• stuck (when not updated over 1hr),

• no_runner.

Proposal

Prepare a new enum failure_reason on ci_builds and tie it with build.drop!/job.drop!.

/cc @ayufan