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/context/access_log.go

@@ -27,7 +27,7 @@ var signedUserNameStringPointerKey interface{} = "signedUserNameStringPointerKey
 // AccessLogger returns a middleware to log access logger
 func AccessLogger() func(http.Handler) http.Handler {
 	logger := log.GetLogger("access")
-	logTemplate, _ := template.New("log").Parse(setting.AccessLogTemplate)
+	logTemplate, _ := template.New("log").Parse(setting.Log.AccessLogTemplate)
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
 			start := time.Now()