feat: support evaluation of concurrency clauses in runner (#827)

Pre-req for support `concurrency` clauses for Gitea Actions, later added to Gitea in PR: https://github.com/go-gitea/gitea/pull/32751. Unit tests added in this PR relative to upstream.

Squashes PRs https://gitea.com/gitea/act/pulls/124 & https://gitea.com/gitea/act/pulls/139, as noted in https://code.forgejo.org/forgejo/runner/issues/678

Reviewed-on: https://gitea.com/gitea/act/pulls/124
Reviewed-by: Lunny Xiao <lunny@noreply.gitea.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-committed-by: Zettat123 <zettat123@gmail.com>
Reviewed-on: https://gitea.com/gitea/act/pulls/139
Reviewed-by: Zettat123 <zettat123@noreply.gitea.com>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: ChristopherHX <christopher.homberger@web.de>
Co-committed-by: ChristopherHX <christopher.homberger@web.de>

<!--start release-notes-assistant-->
<!--URL:https://code.forgejo.org/forgejo/runner-->
- features
  - [PR](https://code.forgejo.org/forgejo/runner/pulls/827): <!--number 827 --><!--line 0 --><!--description ZmVhdDogc3VwcG9ydCBldmFsdWF0aW9uIG9mIGNvbmN1cnJlbmN5IGNsYXVzZXMgaW4gcnVubmVy-->feat: support evaluation of concurrency clauses in runner<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://code.forgejo.org/forgejo/runner/pulls/827
Reviewed-by: earl-warren <earl-warren@noreply.code.forgejo.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>

act/jobparser/jobparser_test.go

@@ -42,6 +42,16 @@ func TestParse(t *testing.T) {
 			options: nil,
 			wantErr: false,
 		},
+		{
+			name:    "job_concurrency",
+			options: nil,
+			wantErr: false,
+		},
+		{
+			name:    "job_concurrency_eval",
+			options: nil,
+			wantErr: false,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {