Add suspend/resume support to GitLab

What does this MR do and why?

Summary

• Adds a suspend_options field to the runner job response JSON, carrying suspend_on_success, suspend_on_failure, and environment_key from build.options
• Introduces a pipeline creation chain path for suspend_options: RunWorkloadService → CreatePipelineService → Chain::Command → Seed::Context → Seed::Build → JobDefinition
• Extends WorkloadDefinition with suspension attrs so workloads can request environment suspension programmatically

Problem

Suspension triggers and the resume key were previously carried as CI variables (CI_SUSPEND_ON_SUCCESS, CI_SUSPEND_ON_FAILURE, CI_SUSPENDABLE_ENVIRONMENT_RESUME_KEY). Per the suspendable environments blueprint, these are internal job plumbing — not user-visible, not overridable by group/project settings, and not subject to CI variable inheritance. They belong in build.options, set by the pipeline creation chain.

Solution

Read side (presenter + entity):

• BuildRunnerPresenter#suspend_options reads from build.options and returns a hash
• Response entity exposes suspend_options conditionally (only when present)

Write side (pipeline creation chain):

• WorkloadDefinition carries suspend_on_success, suspend_on_failure, environment_key as attrs (not in to_job_hash — these are not CI YAML keys)
• RunWorkloadService builds a suspend_options hash and passes it to CreatePipelineService
• CreatePipelineService#extra_options whitelists suspend_options and puts it on Chain::Command
• Chain::Seed passes command.suspend_options into Seed::Context
• Seed::Build#attributes deep-merges { options: context.suspend_options } into the build, following the same pattern as inputs_attributes
• Options land in JobDefinition (immutable) through the normal Processable.fabricate path

JSON schema:

• build_metadata_config_options.json updated to allow suspend_on_success (boolean), suspend_on_failure (boolean), and environment_key (string)

Wire format

{
  "suspend_options": {
    "suspend_on_success": true,
    "suspend_on_failure": false,
    "environment_key": "runner-abc/acquisition-key=\"uuid-123\""
  }
}

References

• Epic: Resumable Jobs for CI and Agent Sessions (gitlab-org#21159)
• Blueprint: Blueprint - Resumable Jobs for CI and Agent Ses... (#593314)

Screenshots or screen recordings

N.A.

How to set up and validate locally

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