Implement last opened functionality (#4633)

* Implement last opened functionality

Fixes https://github.com/cdr/code-server/issues/4619

* Fix test temp dirs not being cleaned up

* Mock logger everywhere

This suppresses all the error and debug output we generate which makes
it hard to actually find which test has failed.  It also gives us a
standard way to test logging for the few places we do that.

* Use separate data directories for unit test instances

Exactly as we do for the e2e tests.

* Add integration tests for vscode route

* Make settings use --user-data-dir

Without this test instances step on each other feet and they also
clobber your own non-test settings.

* Make redirects consistent

They will preserve the trailing slash if there is one.

* Remove compilation check

If you do a regular non-watch build there are no compilation stats so
this bricks VS Code in CI when running the unit tests.

I am not sure how best to fix this for the case where you have a build
that has not been packaged yet so I just removed it for now and added a
message to check if VS Code is compiling when in dev mode.

* Update code-server update endpoint name

test/unit/helpers.test.ts

@@ -1,12 +1,16 @@
 import { promises as fs } from "fs"
-import { getAvailablePort, tmpdir, useEnv } from "../../test/utils/helpers"
+import { clean, getAvailablePort, tmpdir, useEnv } from "../../test/utils/helpers"
 
 /**
  * This file is for testing test helpers (not core code).
  */
 describe("test helpers", () => {
+  const testName = "temp-dir"
+  beforeAll(async () => {
+    await clean(testName)
+  })
+
   it("should return a temp directory", async () => {
-    const testName = "temp-dir"
     const pathToTempDir = await tmpdir(testName)
     expect(pathToTempDir).toContain(testName)
     expect(fs.access(pathToTempDir)).resolves.toStrictEqual(undefined)