Stale files within `fn/` do not get deleted

[Ionaru]

Description

Stale API function files within fn/ do not get deleted when the API that was previously generated is now excluded or deleted.

Repro:

1. Generate a new client using default settings and this schema:

openapi: 3.1.0
info:
  title: Delete test
  version: "1"
paths:
  /first-path:
    get:
      tags:
        - pet
  /second-path:
    get:
      tags:
        - store

It generated src\app\api\fn\pet\first-path-get.ts and src\app\api\fn\store\second-path-get.ts.

2. Modify the schema (delete the second path)

openapi: 3.1.0
info:
  title: Delete test
  version: "2"
paths:
  /first-path:
    get:
      tags:
        - pet

3. Regenerate using the default settings

Both src\app\api\fn\pet\first-path-get.ts and src\app\api\fn\store\second-path-get.ts still exist while src\app\api\fn\store\second-path-get.ts should have been deleted.

This also seems to happen with models in models/.

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Workaround

We currently remove the entire generated folder using rimraf before regenerating it.