docs(cmek): update with features and info

[GMartinez-Sisti]

• Make docs agnostic to KMS provider
• Add supported providers
• Add backup/restore
• Add rotate key
• Add performance details

[robot-clickhouse]

This is an automated comment for commit b02e193 with description of existing statuses. It's updated for the latest CI running

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[johnnymatthews]

No idea why the line 64 is freaking out GitHub's markdown linter. Pushed a couple of "fixes" but GitHub is still not having a good time. Ah well. The rest of this PR looks good to me.

[GMartinez-Sisti]

@krithika-ch please take a look when possible.