Refactor sha1 and time-limited code (#31023)

Remove "EncodeSha1", it shouldn't be used as a general purpose hasher
(just like we have removed "EncodeMD5" in #28622)

Rewrite the "time-limited code" related code and write better tests, the
old code doesn't seem quite right.

(cherry picked from commit fb1ad920b769799aa1287441289d15477d9878c5)

Conflicts:
	modules/git/utils_test.go
	trivial context conflict because sha256 testing in Forgejo has diverged

modules/git/utils.go

@@ -4,6 +4,8 @@
 package git
 
 import (
+	"crypto/sha1"
+	"encoding/hex"
 	"fmt"
 	"io"
 	"os"
@@ -128,3 +130,9 @@ func (l *LimitedReaderCloser) Read(p []byte) (n int, err error) {
 func (l *LimitedReaderCloser) Close() error {
 	return l.C.Close()
 }
+
+func HashFilePathForWebUI(s string) string {
+	h := sha1.New()
+	_, _ = h.Write([]byte(s))
+	return hex.EncodeToString(h.Sum(nil))
+}