snapcraft expand-extensions is broken

[Scarlett Gately Moore]

snapcraft expand-extensions > snapcraft-expanded.yaml Bad snapcraft.yaml content:

    extra field ‘parse-info’ not permitted in ‘parts.blinken’ configuration

[Callahan Kovacs (mr-cal)]

I was able to reproduce this failure with:

```
name: expand-extensions
base: core22
version: '0.1'
summary: "Test `expand-extensions` can successfully parse the snapcraf.yaml."
description: |
  This snapcraft.yaml includes regression tests where extensions, parse-info,
  and advanced grammar are not parsed before expanding extensions.

grade: stable
confinement: strict

apps:
  list-plugins:
    command: /bin/true
    extensions: [gnome]

parts:
  nil:
    plugin: nil
    parse-info:
    - usr/share/metainfo/photos.ansel.app.appdata.xml
    stage-packages:
      - mesa-opencl-icd
      - ocl-icd-libopencl1
      - on amd64:
          - intel-opencl-icd
```

This reproducer exposes a few failure points - advanced grammar, an extension, and parse-info.

Recently, we fixed a similar bug for the `snapcraft list-plugins` command. (https://github.com/snapcore/snapcraft/pull/4035)

It looks like that same fix needs to be applied `snapcraft expand-extensions`.

Originally reported here: https://forum.snapcraft.io/t/parts-part-parse-info-broken/34335