Reducing the filestore dependencies from the rest of the source code (#16816)

* Reducing the filestore dependencies from the rest of the source code

* Making more generic config conversion to FileBackendSettings

* Fixing usage of the NewFileBackend function

* Fixing more usages of the NewFileBackend function

* Fix some linter errors

* Fix more linter errors

* Fixing some unit tests

* Fixing linter problem

* Addressing PR review comments

* Simplifing the CopyFile for tests

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/server.go

@@ -1568,7 +1568,7 @@ func (s *Server) stopSearchEngine() {
 
 func (s *Server) FileBackend() (filesstore.FileBackend, *model.AppError) {
 	license := s.License()
-	backend, err := filesstore.NewFileBackend(&s.Config().FileSettings, license != nil && *license.Features.Compliance)
+	backend, err := filesstore.NewFileBackend(s.Config().FileSettings.ToFileBackendSettings(license != nil && *license.Features.Compliance))
 	if err != nil {
 		return nil, model.NewAppError("FileBackend", "api.file.no_driver.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}