PlugOS refactor and other tweaks (#631)

* Prep for in-process plug loading (e.g. for CF workers, Deno Deploy)
* Prototype of fixed in-process loading plugs
* Fix: buttons not to scroll with content
* Better positioning of modal especially on mobile
* Move query caching outside query
* Fix annoying mouse behavior when filter box appears
* Page navigator search tweaks

plug-api/lib/memory_cache.test.ts

@@ -0,0 +1,17 @@
+import { sleep } from "$sb/lib/async.ts";
+import { ttlCache } from "$sb/lib/memory_cache.ts";
+import { assertEquals } from "../../test_deps.ts";
+
+Deno.test("Memory cache", async () => {
+  let calls = 0;
+  async function expensiveFunction(key: string) {
+    calls++;
+    await sleep(1);
+    return key;
+  }
+  assertEquals("key", await ttlCache("key", expensiveFunction, 0.01));
+  assertEquals(1, calls);
+  assertEquals("key", await ttlCache("key", expensiveFunction, 0.01));
+  assertEquals(1, calls);
+  await sleep(10);
+});