Replace custom Go formatter with golangci-lint fmt (#37194)

Use `golangci-lint fmt` to format code, replacing the previous custom
formatter tool. https://github.com/daixiang0/gci is used to order the
imports.

`make fmt` performs ~13% faster while consuming ~57% less cpu while
formatting for me.

`GOFUMPT_PACKAGE` is gone because it's using the builtin package from
golangci-lint.

Co-authored-by: Claude (claude-opus-4-6) <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

.github/workflows/pull-compliance.yml

@@ -122,7 +122,7 @@ jobs:
           go-version-file: go.mod
           check-latest: true
       - run: make deps-backend deps-tools
-      - run: make lint-go-windows lint-go-gitea-vet
+      - run: make lint-go-windows
         env:
           TAGS: bindata sqlite sqlite_unlock_notify
           GOOS: windows