COMMAND GETKEYS support

[AvitalFineRedis]

Pull Request check-list

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• Does $ tox pass with this change (including linting)?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?

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afterwards / while the PR is open.

Description of change

Add support to redis command COMMAND GETKEYS