stream_edit: Convert module to typescript.

tools/test-js-with-node

@@ -243,7 +243,7 @@ EXEMPT_FILES = make_set(
         "web/src/stream_color_events.ts",
         "web/src/stream_create.ts",
         "web/src/stream_create_subscribers.ts",
-        "web/src/stream_edit.js",
+        "web/src/stream_edit.ts",
         "web/src/stream_edit_subscribers.ts",
         "web/src/stream_edit_toggler.ts",
         "web/src/stream_list.ts",

web/src/peer_data.ts

@@ -43,7 +43,7 @@ export function potential_subscribers(stream_id: number): User[] {
         stream.  This may include some bots.
 
         We currently use it for typeahead in
-        stream_edit.js.
+        stream_edit.ts.
 
         This may be a superset of the actual
         subscribers that you can change in some cases

web/src/settings_org.ts

@@ -801,7 +801,7 @@ export function save_organization_settings(
     data: Record<string, string | number | boolean>,
     $save_button: JQuery,
     patch_url: string,
-    success_continuation: (() => void) | undefined,
+    success_continuation: (() => void) | undefined = undefined,
 ): void {
     const $subsection_parent = $save_button.closest(".settings-subsection-parent");
     const $save_btn_container = $subsection_parent.find(".save-button-controls");