Uniform all temporary directories and allow customizing temp path (#32352)

This PR uniform all temporary directory usage so that it will be easier
to manage.

Relate to #31792 

- [x] Added a new setting to allow users to configure the global
temporary directory.
- [x] Move all temporary files and directories to be placed under
os.Temp()/gitea.
- [x] `setting.Repository.Local.LocalCopyPath` now will be
`setting.TempPath/local-repo` and the customized path is removed.
```diff
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;[repository.local]
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;
-;; Path for local repository copy. Defaults to  TEMP_PATH + `local-repo`, this is deprecated and cannot be changed
-;LOCAL_COPY_PATH = local-repo
```

- [x] `setting.Repository.Upload.TempPath` now will be
`settting.TempPath/uploads` and the customized path is removed.
```diff
;[repository.upload]
-;;
-;; Path for uploads. Defaults to TEMP_PATH + `uploads`
-;TEMP_PATH = uploads
```

- [x] `setting.Packages.ChunkedUploadPath` now will be
`settting.TempPath/package-upload` and the customized path is removed.
```diff
;[packages]
-;;
-;; Path for chunked uploads. Defaults it's `package-upload` under `TEMP_PATH` unless it's an absolute path.
-;CHUNKED_UPLOAD_PATH = package-upload
```

- [x] `setting.SSH.KeyTestPath` now will be
`settting.TempPath/ssh_key_test` and the customized path is removed.
```diff
[server]
-;;
-;; Directory to create temporary files in when testing public keys using ssh-keygen,
-;; default is the system temporary directory.
-;SSH_KEY_TEST_PATH =
```

TODO:
- [ ] setting.PprofDataPath haven't been changed because it may need to
be kept until somebody read it but temp path may be clean up any time.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/setting/server.go

@@ -7,6 +7,7 @@ import (
 	"encoding/base64"
 	"net"
 	"net/url"
+	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -59,6 +60,8 @@ var (
 	// AssetVersion holds a opaque value that is used for cache-busting assets
 	AssetVersion string
 
+	appTempPathInternal string // the temporary path for the app, it is only an internal variable, do not use it, always use AppDataTempDir
+
 	Protocol                   Scheme
 	UseProxyProtocol           bool // `ini:"USE_PROXY_PROTOCOL"`
 	ProxyProtocolTLSBridging   bool //`ini:"PROXY_PROTOCOL_TLS_BRIDGING"`
@@ -330,6 +333,19 @@ func loadServerFrom(rootCfg ConfigProvider) {
 	if !filepath.IsAbs(AppDataPath) {
 		AppDataPath = filepath.ToSlash(filepath.Join(AppWorkPath, AppDataPath))
 	}
+	if IsInTesting && HasInstallLock(rootCfg) {
+		// FIXME: in testing, the "app data" directory is not correctly initialized before loading settings
+		if _, err := os.Stat(AppDataPath); err != nil {
+			_ = os.MkdirAll(AppDataPath, os.ModePerm)
+		}
+	}
+
+	appTempPathInternal = sec.Key("APP_TEMP_PATH").String()
+	if appTempPathInternal != "" {
+		if _, err := os.Stat(appTempPathInternal); err != nil {
+			log.Fatal("APP_TEMP_PATH %q is not accessible: %v", appTempPathInternal, err)
+		}
+	}
 
 	EnableGzip = sec.Key("ENABLE_GZIP").MustBool()
 	EnablePprof = sec.Key("ENABLE_PPROF").MustBool(false)