feat(actions): implement jobs.<job_id>.continue-on-error (#38100)

Support `continue-on-error` for workflow jobs when aggregating an
Actions workflow run status.

Previously, `continue-on-error` was parsed from workflow YAML but was
not persisted or used when calculating the overall run result. As a
result, a failed job could incorrectly fail the entire workflow even
when the workflow explicitly allowed that job to fail.

This PR stores the parsed `continue-on-error` value on each action run
job and treats failed jobs with `continue-on-error: true` as successful
when computing the workflow run status, matching GitHub Actions
behavior.

## Changes

- Add `ContinueOnError` to `jobparser.Job`.
- Add `continue_on_error` to `ActionRunJob` with a `NOT NULL DEFAULT
FALSE` migration.
- Populate `ActionRunJob.ContinueOnError` when creating workflow run
jobs.
- Update workflow status aggregation so failed `continue-on-error` jobs
do not fail the overall run.
- Leave `resolveCheckNeeds` unchanged so dependent jobs still see the
job result as `failure` and are skipped by default.

## Compatibility

This is backward compatible.

If only the runner or only the server is updated, `continue-on-error`
continues to degrade to the previous behavior and is effectively ignored
until both sides support it.

Related runner PR: https://gitea.com/gitea/runner/pulls/1032

---------

Signed-off-by: bircni <bircni@icloud.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/actions/jobparser/testdata/continue_on_error_expr.in.yaml

@@ -0,0 +1,10 @@
+name: test
+jobs:
+  job1:
+    strategy:
+      matrix:
+        experimental: [false, true]
+    runs-on: ubuntu-22.04
+    continue-on-error: ${{ matrix.experimental }}
+    steps:
+      - run: echo hi