Minor documentation issues in Control API

[mattheworiordan]

See https://ably.com/docs/account/control-api.

1. Wording needs improving at the outset:

2. Diagram may need reviewing?

3. No mention of Terraform

Given Ably's Terraform dominates control API usage and is arguably the recommended approach for infrastructure integration, it deserves a big call out here, long before OpenAPI IMHO.

4. Mention of Control API for stats is inconsistent

See screenshot below. Issues are:

• Control API mention is inconsistent with remaining stats docs on how to access states (why is it mentioned at the top)
• App and account stats docs are inconsistent
• Documentation around fields is not up to date with latest schema

5. Whilst you're at it, screenshots could be updated :) Nav is wrong, and capabilities have been extended (to include stats).

6. Instructions on how to find your account ID and app ID don't use the control API to get this info?

See https://ably.com/docs/account/control-api#account-id and https://ably.com/docs/account/control-api#app-id. It makes no mention of the /me and /apps/list control API endpoints! We should dogfood our own API for this, and offer that as a secondary option.