Update docgen scripts for v1/v2

[taeold]

Few changes here:

1. Fix docgen script for v1 to work with the new file layout

2. Remove old apidoc scripts - no longer used!

3. Rewrite toc.ts script to fix the "lowercase" issue where every toc title was lowercased. While I fix the issue here, it also changes the overall toc.yaml structure to return to more flatten structure. I think the output looks fine to me, but we should discuss if we find this revert less desirable.

toc:
  - title: firebase-functions
    path: /docs/functions/beta/reference/firebase-functions.md
    section:
      - title: Alerts
        path: /docs/functions/beta/reference/firebase-functions.alerts.md
      - title: CloudEvent
        path: /docs/functions/beta/reference/firebase-functions.cloudevent.md
      - title: CloudFunction
        path: /docs/functions/beta/reference/firebase-functions.cloudfunction.md
      - title: Database
        path: /docs/functions/beta/reference/firebase-functions.database.md
      - title: Eventarc
        path: /docs/functions/beta/reference/firebase-functions.eventarc.md
      - title: EventHandlerOptions
        path: >-
          /docs/functions/beta/reference/firebase-functions.eventhandleroptions.md
      - title: GlobalOptions
        path: /docs/functions/beta/reference/firebase-functions.globaloptions.md
      - title: Https
        path: /docs/functions/beta/reference/firebase-functions.https.md
      - title: Identity
        path: /docs/functions/beta/reference/firebase-functions.identity.md
      - title: Logger
        path: /docs/functions/beta/reference/firebase-functions.logger.md
      - title: Pubsub
        path: /docs/functions/beta/reference/firebase-functions.pubsub.md
      - title: Storage
        path: /docs/functions/beta/reference/firebase-functions.storage.md
      - title: Tasks
        path: /docs/functions/beta/reference/firebase-functions.tasks.md

[taeold]

Since @egilmorez is OOO this week and this code change does not affect production code, will merge w/o approval.