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/indexer/issues/indexer_test.go

@@ -27,11 +27,11 @@ func TestMain(m *testing.M) {
 
 func TestBleveSearchIssues(t *testing.T) {
 	assert.NoError(t, unittest.PrepareTestDatabase())
-	setting.Cfg = ini.Empty()
+	setting.CfgProvider = ini.Empty()
 
 	tmpIndexerDir := t.TempDir()
 
-	setting.Cfg.Section("queue.issue_indexer").Key("DATADIR").MustString(path.Join(tmpIndexerDir, "issues.queue"))
+	setting.CfgProvider.Section("queue.issue_indexer").Key("DATADIR").MustString(path.Join(tmpIndexerDir, "issues.queue"))
 
 	oldIssuePath := setting.Indexer.IssuePath
 	setting.Indexer.IssuePath = path.Join(tmpIndexerDir, "issues.queue")
@@ -40,7 +40,7 @@ func TestBleveSearchIssues(t *testing.T) {
 	}()
 
 	setting.Indexer.IssueType = "bleve"
-	setting.NewQueueService()
+	setting.LoadQueueSettings()
 	InitIssueIndexer(true)
 	defer func() {
 		indexer := holder.get()