feat: add ability to delete redis keys on demand

[ecita]

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Description

We are faced with a usecase that requires us to delete specific redis key(s) on demand to manipulate the rate limiting behaviour.

This PR adds del function to limitd client interface in a manner that is aligned with the original Redis DEL function.
https://redis.io/docs/latest/commands/del/

Testing

• This change adds test coverage for new/changed/fixed functionality

Checklist

• I have added documentation for new/changed functionality in this PR or in auth0.com/docs
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not the default branch