refactor: drop logrus and other direct dependencies (#1319)

After https://gitea.com/gitea/runner/pulls/1304, logrus stayed only to forward logs from docker/cli and moby/go-archive. The runner used a small part of those: volume parsing, the build context tar, the `ssh://` connection and registry credentials. Own code that matches them replaces them, so logrus leaves the module graph. docker/cli stays for its logrus-free `opts` and `connhelper/ssh` packages.

Other dependencies that the standard library or existing ones cover go too: mergo, httprouter (replaced by `http.ServeMux`), retry-go, go-isatty, go-selinux, container-device-interface, gotest.tools and go-cmp (replaced by testify). The binary shrinks by 5%.

Behaviour differences:

1. An unreadable file in a build context is skipped with a warning, where go-archive left a truncated tar.
2. Build contexts no longer carry `security.capability` xattrs.
3. The cache and artifact servers answer HEAD on GET routes, and no longer redirect trailing slashes or answer OPTIONS.

*Written by Claude.*

---------

Co-authored-by: bircni <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1319
Reviewed-by: bircni <[email protected]>
Reviewed-by: Lunny Xiao <[email protected]>
Co-authored-by: silverwind <[email protected]>

internal/pkg/report/reporter_test.go

@@ -15,6 +15,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"testing"
+	"testing/synctest"
 	"time"
 
 	"gitea.com/gitea/runner/act/common/logging"
@@ -1161,6 +1162,19 @@ func TestReporter_EffectiveCloseTimeout(t *testing.T) {
 	assert.Equal(t, 5*time.Second, (&Reporter{closeTimeout: 5 * time.Second}).effectiveCloseTimeout())
 }
 
+func TestReporter_FlushFinalRetriesUntilSuccess(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		calls := 0
+		require.NoError(t, (&Reporter{}).flushFinal(func() error {
+			if calls++; calls < 3 {
+				return errors.New("unavailable")
+			}
+			return nil
+		}))
+		assert.Equal(t, 3, calls)
+	})
+}
+
 func TestReporter_ParseResult(t *testing.T) {
 	r := &Reporter{}