Refactor the setting to make unit test easier (#22405)

Some bugs caused by less unit tests in fundamental packages. This PR
refactor `setting` package so that create a unit test will be easier
than before.

- All `LoadFromXXX` files has been splited as two functions, one is
`InitProviderFromXXX` and `LoadCommonSettings`. The first functions will
only include the code to create or new a ini file. The second function
will load common settings.
- It also renames all functions in setting from `newXXXService` to
`loadXXXSetting` or `loadXXXFrom` to make the function name less
confusing.
- Move `XORMLog` to `SQLLog` because it's a better name for that.

Maybe we should finally move these `loadXXXSetting` into the `XXXInit`
function? Any idea?

---------

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: delvh <dev.lh@web.de>

modules/setting/mirror.go

@@ -24,16 +24,16 @@ var Mirror = struct {
 	DefaultInterval: 8 * time.Hour,
 }
 
-func newMirror() {
+func loadMirrorFrom(rootCfg ConfigProvider) {
 	// Handle old configuration through `[repository]` `DISABLE_MIRRORS`
 	// - please note this was badly named and only disabled the creation of new pull mirrors
 	// FIXME: DEPRECATED to be removed in v1.18.0
-	deprecatedSetting("repository", "DISABLE_MIRRORS", "mirror", "ENABLED")
-	if Cfg.Section("repository").Key("DISABLE_MIRRORS").MustBool(false) {
+	deprecatedSetting(rootCfg, "repository", "DISABLE_MIRRORS", "mirror", "ENABLED")
+	if rootCfg.Section("repository").Key("DISABLE_MIRRORS").MustBool(false) {
 		Mirror.DisableNewPull = true
 	}
 
-	if err := Cfg.Section("mirror").MapTo(&Mirror); err != nil {
+	if err := rootCfg.Section("mirror").MapTo(&Mirror); err != nil {
 		log.Fatal("Failed to map Mirror settings: %v", err)
 	}