Add state content component (#21370)

* Move state content into its own component for reusability

* Add entity state content selector

* Use live timer

* Rename live timer to remaining time and remove remaining attribute from state content list

* Move default in state content component

* Fix picker

src/components/ha-selector/ha-selector.ts

@@ -57,6 +57,7 @@ const LOAD_ELEMENTS = {
   color_temp: () => import("./ha-selector-color-temp"),
   ui_action: () => import("./ha-selector-ui-action"),
   ui_color: () => import("./ha-selector-ui-color"),
+  ui_state_content: () => import("./ha-selector-ui-state-content"),
 };
 
 const LEGACY_UI_SELECTORS = new Set(["ui-action", "ui-color"]);