Uniform all temporary directories and allow customizing temp path

[lunny]

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

Relate to #31792

• Added a new setting to allow users to configure the global temporary directory.
• Move all temporary files and directories to be placed under os.Temp()/gitea.
• setting.Repository.Local.LocalCopyPath now will be setting.TempPath/local-repo and the customized path is removed.

-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-;[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

• setting.Repository.Upload.TempPath now will be settting.TempPath/uploads and the customized path is removed.

;[repository.upload]
-;;
-;; Path for uploads. Defaults to TEMP_PATH + `uploads`
-;TEMP_PATH = uploads

• setting.Packages.ChunkedUploadPath now will be settting.TempPath/package-upload and the customized path is removed.

;[packages]
-;;
-;; Path for chunked uploads. Defaults it's `package-upload` under `TEMP_PATH` unless it's an absolute path.
-;CHUNKED_UPLOAD_PATH = package-upload

• setting.SSH.KeyTestPath now will be settting.TempPath/ssh_key_test and the customized path is removed.

[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.

[wxiaoguang]

Feel free to complete RemoveOutdated and add more tests for TempDir

[wxiaoguang]

Does the new change look good to you?

[lunny]

Does the new change look good to you?

Looks good to me except left tasks.