fix(actions): keep the caller's event and inputs in reusable workflow jobs (#39452)

Fixes https://github.com/go-gitea/gitea/issues/38705
Fixes https://gitea.com/gitea/runner/issues/1232

Jobs of a called workflow saw `gitea.event_name` as `workflow_call` and
`gitea.event.inputs` replaced by the caller's `with:`, so a condition
like `gitea.event_name == 'push'` never held in them, and a dispatched
run's own inputs were lost there.

They now keep the caller's trigger event and their `inputs` are the
run's `workflow_dispatch` inputs overlaid with the caller's `with:`, as
on GitHub. For example, with `workflow_dispatch` inputs `{target: prod,
debug: true}` and caller's `with: {target: dev}`, the called workflow's
`inputs` are `{target: dev, debug: true}`.

A runner cannot resolve these inputs itself, so they are sent in a new
`gitea_workflow_call` context entry, with the original event name and
inputs for the runner to restore. For more details, see the runner PR:
https://gitea.com/gitea/runner/pulls/1250

Co-authored-by: silverwind <me@silverwind.io>

models/actions/run_job.go

@@ -116,7 +116,7 @@ type ActionRunJob struct {
 	//   - JSON object  : explicit mapping {alias: source_name}; names only, no values.
 	// Only set when IsReusableCaller is true.
 	CallSecrets string `xorm:"LONGTEXT"`
-	// CallPayload is the JSON-encoded WorkflowCallPayload exposed to children as gitea.event.
+	// CallPayload is the JSON-encoded WorkflowCallPayload.
 	// Populated atomically with IsExpanded at the end of expandReusableWorkflowCaller.
 	// Only set when IsReusableCaller is true.
 	CallPayload string `xorm:"LONGTEXT"`