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/webhook.go

@@ -29,8 +29,8 @@ var Webhook = struct {
 	ProxyHosts:     []string{},
 }
 
-func newWebhookService() {
-	sec := Cfg.Section("webhook")
+func loadWebhookFrom(rootCfg ConfigProvider) {
+	sec := rootCfg.Section("webhook")
 	Webhook.QueueLength = sec.Key("QUEUE_LENGTH").MustInt(1000)
 	Webhook.DeliverTimeout = sec.Key("DELIVER_TIMEOUT").MustInt(5)
 	Webhook.SkipTLSVerify = sec.Key("SKIP_TLS_VERIFY").MustBool()