enhance: support client certificates for mutual TLS (#1273)

Add `runner.client_cert_file` and `runner.client_key_file` for Gitea instances that require mutual TLS. The runner presents the certificate on its RPCs, job summary uploads, and the action, reusable workflow and `builtin:checkout` clones from the instance. The files are read on use, so renewed certificates apply without a restart. Job steps do not get them. An incomplete or mismatched pair fails startup.

Clones now decide the token, client certificate and `runner.insecure` with one host check, which also gives reusable workflow clones the TLS settings they lacked. `runner.insecure` still only covers the registered address.

Fixes: https://gitea.com/gitea/runner/issues/321
Co-authored-by: silverwind <[email protected]>
Co-authored-by: silverwind <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1273
Reviewed-by: silverwind <[email protected]>
Co-authored-by: bircni <[email protected]>

e2e/runner_harness.go

@@ -75,7 +75,7 @@ func startRunner(t *testing.T, repo, labelName string, options runnerOptions) *p
 	}
 	labelNames := []string{label.Name}
 
-	pingCli := client.New(fixture.baseURL, cfg.Runner.Insecure, "", "", config.RequestTimeout, cfg.Runner.ExtraHeaders)
+	pingCli := client.New(fixture.baseURL, cfg.Runner.TLSConfig(), "", "", config.RequestTimeout, cfg.Runner.ExtraHeaders)
 	if _, err := pingCli.Ping(ctx, connect.NewRequest(&pingv1.PingRequest{Data: t.Name()})); err != nil {
 		t.Fatalf("ping %s: %v", fixture.baseURL, err)
 	}
@@ -105,7 +105,7 @@ func startRunner(t *testing.T, repo, labelName string, options runnerOptions) *p
 		Ephemeral: regResp.Msg.Runner.Ephemeral,
 	}
 
-	cli := client.New(fixture.baseURL, cfg.Runner.Insecure, reg.UUID, reg.Token, config.RequestTimeout, cfg.Runner.ExtraHeaders)
+	cli := client.New(fixture.baseURL, cfg.Runner.TLSConfig(), reg.UUID, reg.Token, config.RequestTimeout, cfg.Runner.ExtraHeaders)
 
 	runner := run.NewRunner(cfg, reg, cli)
 	declResp, err := runner.Declare(ctx, labelNames)