[MM-32390] Config logic refactor (#17578)

* Replace config generator

* Cleanup

* Some renaming and docs additions to add clarity

* Cleanup logging related methods

* Cleanup emitter

* Fix TestDefaultsGenerator

* Move feature flags synchronization logic out of config package

* Remove unnecessary util functions

* Simplify load/set logic

* Refine semantics and add some test to cover them

* Remove unnecessary deep copies

* Improve logic further

* Fix license header

* Review file store tests

* Fix test

* Fix test

* Avoid additional write during initialization

* More consistent naming

* Update app/feature_flags.go

Co-authored-by: Christopher Speller <crspeller@gmail.com>

* Update config/store.go

Co-authored-by: Christopher Speller <crspeller@gmail.com>

* Update config/store.go

Co-authored-by: Christopher Speller <crspeller@gmail.com>

* Update config/store.go

Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

* Move FF synchronizer to its own package

* Remove unidiomatic use of sync.Once

* Add some comments

* Rename function

* More comment

Co-authored-by: Christopher Speller <crspeller@gmail.com>
Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

Makefile

@@ -549,7 +549,7 @@ config-ldap: ## Configures LDAP.
 config-reset: ## Resets the config/config.json file to the default.
 	@echo Resetting configuration to default
 	rm -f config/config.json
-	OUTPUT_CONFIG=$(PWD)/config/config.json $(GO) generate $(GOFLAGS) ./config
+	OUTPUT_CONFIG=$(PWD)/config/config.json $(GO) $(GOFLAGS) run ./scripts/config_generator
 
 diff-config: ## Compares default configuration between two mattermost versions
 	@./scripts/diff-config.sh