Support VSCode `source.fixAll`.

**Describe the bug**
In a project with a `.vscode/settings.json` file:
```json
{
  "editor.codeActionsOnSave": {
    "source.fixAll": "explicit",
  }
}
```
This will not run `custom_lint` quick fixes on save, but successfully runs quick fixes of the base `analyzer`

**To Reproduce**
Any custom lint that has a quick fix.

**Expected behavior**
The most important quick fix should run
