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>

routers/install/install.go

@@ -134,7 +134,7 @@ func Install(ctx *context.Context) {
 	form.SSHPort = setting.SSH.Port
 	form.HTTPPort = setting.HTTPPort
 	form.AppURL = setting.AppURL
-	form.LogRootPath = setting.LogRootPath
+	form.LogRootPath = setting.Log.RootPath
 
 	// E-mail service settings
 	if setting.MailService != nil {
@@ -467,7 +467,7 @@ func SubmitInstall(ctx *context.Context) {
 	cfg.Section("session").Key("PROVIDER").SetValue("file")
 
 	cfg.Section("log").Key("MODE").SetValue("console")
-	cfg.Section("log").Key("LEVEL").SetValue(setting.LogLevel.String())
+	cfg.Section("log").Key("LEVEL").SetValue(setting.Log.Level.String())
 	cfg.Section("log").Key("ROOT_PATH").SetValue(form.LogRootPath)
 	cfg.Section("log").Key("ROUTER").SetValue("console")