Deprecate `ColorPicker` and move away from using `DeprecatedDropdown`

[frankieyan]

🚀 Feature request

Reported in https://github.com/Doist/reactist/pull/680#discussion_r945869248

The ColorPicker is built using the now-deprecated Dropdown component (see https://github.com/Doist/reactist/pull/680). To be able to remove the component, it needs to be re-implemented using the Menu component, or another equivalent.

This is currently used for the channel colour picker in Twist:

Possible implementations

Reakit's menu supported two-dimensional menus using a CompositeGroup. It is likely this is still supported in Ariakit.