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>

cmd/dump_repo.go

@@ -94,7 +94,7 @@ func runDumpRepository(ctx *cli.Context) error {
 	log.Info("AppPath: %s", setting.AppPath)
 	log.Info("AppWorkPath: %s", setting.AppWorkPath)
 	log.Info("Custom path: %s", setting.CustomPath)
-	log.Info("Log path: %s", setting.LogRootPath)
+	log.Info("Log path: %s", setting.Log.RootPath)
 	log.Info("Configuration file: %s", setting.CustomConf)
 
 	var (