Cfg: Add a setting to configure if the local file system is available (#83616)

* Introduce environment.local_filesystem_available

* Only show TLS client cert, client key, client ca when local_filesystem_available is true

* Rename LocalFSAvailable to LocalFileSystemAvailable

pkg/api/dtos/frontend_settings.go

@@ -260,4 +260,6 @@ type FrontendSettingsDTO struct {
 	// Enterprise
 	Licensing     *FrontendSettingsLicensingDTO     `json:"licensing,omitempty"`
 	Whitelabeling *FrontendSettingsWhitelabelingDTO `json:"whitelabeling,omitempty"`
+
+	LocalFileSystemAvailable bool `json:"localFileSystemAvailable"`
 }