- Part of issue 16323.
- Previously this was being done manually by Cask maintainers.
- While we're here, enforce that the `zap trash` path is not in `[]` if
  it only contains a single element.
- This is buggy on actual Casks, hence the draft PR.

- Interpolating the version into a path is a common pattern, but the interpolations
  trip up the alphabetization autocorrect quite spectacularly, so let's
  ignore them (for now?).

- Use `sort_by` to sort the array, rather than comparing each element
  to the next.
- This doesn't error with complaints about clobbering at all when run on
  `homebrew/cask`, hurray. And it also handles interpolations correctly,
  rather than ignoring them.

Co-authored-by: Bevan Kay <email@bevankay.me>

```
  1) Cask::Cask#to_h when loaded from cask file returns expected hash
     Failure/Error: expect(JSON.pretty_generate(hash)).to eq(expected_json)

Diff:
       @@ -28,9 +28,7 @@
              "uninstall": [
                {
                  "launchctl": "com.every.thing.agent",
       -          "delete": [
       -            "/Library/EverythingHelperTools"
       -          ],
       +          "delete": "/Library/EverythingHelperTools",
                  "kext": "com.every.thing.driver",
                  "signal": [
                    [
       @@ -103,7 +101,7 @@
          ],
          "ruby_source_path": "Casks/everything.rb",
          "ruby_source_checksum": {
       -    "sha256": "b2707d1952f02c3fa566b7ad2a707a847a959d36f51d3dee642dbe5deec12f27"
       +    "sha256": "0c4af571cce1632fc6a3dcf3e75ba82a3283077ef12399428192c26f9d6f779b"
          }
        }
     # ./test/cask/cask_spec.rb:225:in `block (4 levels) in <top (required)>'
     # ./test/support/helper/spec/shared_context/homebrew_cask.rb:53:in `block (2 levels) in <top (required)>'
```

Co-authored-by: Bevan J. Kay <email@bevankay.me>

- Since `zap` can have more than just `trash`.