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/mailer_test.go

@@ -10,7 +10,7 @@ import (
 	ini "gopkg.in/ini.v1"
 )
 
-func TestParseMailerConfig(t *testing.T) {
+func Test_loadMailerFrom(t *testing.T) {
 	iniFile := ini.Empty()
 	kases := map[string]*Mailer{
 		"smtp.mydomain.com": {
@@ -34,7 +34,7 @@ func TestParseMailerConfig(t *testing.T) {
 			sec.NewKey("HOST", host)
 
 			// Check mailer setting
-			parseMailerConfig(iniFile)
+			loadMailerFrom(iniFile)
 
 			assert.EqualValues(t, kase.SMTPAddr, MailService.SMTPAddr)
 			assert.EqualValues(t, kase.SMTPPort, MailService.SMTPPort)