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
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.