refactor: replace debounce/throttle deps with first-party code (#38610)

Adds `web_src/js/utils/func.ts` with `debounce` and `throttle`, dropping
`throttle-debounce` and `perfect-debounce` dependencies. Both were
needed before: the former has no promise-returning debounce, which
`TextExpander` requires, and the latter no `throttle`.

Signature follows lodash and es-toolkit: `(func, wait, {leading,
trailing})` plus `cancel`, so argument order flips at the migrated call
sites.

web_src/js/utils/dom.ts

@@ -1,4 +1,4 @@
-import {debounce} from 'throttle-debounce';
+import {debounce} from './func.ts';
 import type {Promisable} from '../types.ts';
 import type $ from 'jquery';
 import {isInFrontendUnitTest} from './testhelper.ts';
@@ -242,7 +242,7 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
 }
 
 export function onInputDebounce(fn: () => Promisable<any>) {
-  return debounce(300, fn);
+  return debounce(fn, 300);
 }
 
 type LoadableElement = HTMLEmbedElement | HTMLIFrameElement | HTMLImageElement | HTMLScriptElement | HTMLTrackElement;