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/cache.go

@@ -49,8 +49,8 @@ var CacheService = struct {
 // MemcacheMaxTTL represents the maximum memcache TTL
 const MemcacheMaxTTL = 30 * 24 * time.Hour
 
-func newCacheService() {
-	sec := Cfg.Section("cache")
+func loadCacheFrom(rootCfg ConfigProvider) {
+	sec := rootCfg.Section("cache")
 	if err := sec.MapTo(&CacheService); err != nil {
 		log.Fatal("Failed to map Cache settings: %v", err)
 	}
@@ -79,7 +79,7 @@ func newCacheService() {
 		Service.EnableCaptcha = false
 	}
 
-	sec = Cfg.Section("cache.last_commit")
+	sec = rootCfg.Section("cache.last_commit")
 	if !CacheService.Enabled {
 		CacheService.LastCommit.Enabled = false
 	}