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/cors.go

@@ -27,12 +27,8 @@ var CORSConfig = struct {
 	XFrameOptions: "SAMEORIGIN",
 }
 
-func newCORSService() {
-	sec := Cfg.Section("cors")
-	if err := sec.MapTo(&CORSConfig); err != nil {
-		log.Fatal("Failed to map cors settings: %v", err)
-	}
-
+func loadCorsFrom(rootCfg ConfigProvider) {
+	mustMapSetting(rootCfg, "cors", &CORSConfig)
 	if CORSConfig.Enabled {
 		log.Info("CORS Service Enabled")
 	}