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>

tests/test_utils.go

@@ -57,7 +57,7 @@ func InitTest(requireGitea bool) {
 	}
 
 	setting.SetCustomPathAndConf("", "", "")
-	setting.LoadForTest()
+	setting.InitProviderAndLoadCommonSettingsForTest()
 	setting.Repository.DefaultBranch = "master" // many test code still assume that default branch is called "master"
 	_ = util.RemoveAll(repo_module.LocalCopyPath())
 
@@ -65,7 +65,7 @@ func InitTest(requireGitea bool) {
 		log.Fatal("git.InitOnceWithSync: %v", err)
 	}
 
-	setting.InitDBConfig()
+	setting.LoadDBSetting()
 	if err := storage.Init(); err != nil {
 		fmt.Printf("Init storage failed: %v", err)
 		os.Exit(1)