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/doctor/paths.go

@@ -67,7 +67,8 @@ func checkConfigurationFiles(ctx context.Context, logger log.Logger, autofix boo
 		return err
 	}
 
-	setting.LoadFromExisting()
+	setting.InitProviderFromExistingFile()
+	setting.LoadCommonSettings()
 
 	configurationFiles := []configurationFile{
 		{"Configuration File Path", setting.CustomConf, false, true, false},
@@ -75,7 +76,7 @@ func checkConfigurationFiles(ctx context.Context, logger log.Logger, autofix boo
 		{"Data Root Path", setting.AppDataPath, true, true, true},
 		{"Custom File Root Path", setting.CustomPath, true, false, false},
 		{"Work directory", setting.AppWorkPath, true, true, false},
-		{"Log Root Path", setting.LogRootPath, true, true, true},
+		{"Log Root Path", setting.Log.RootPath, true, true, true},
 	}
 
 	if options.IsDynamic() {