No way to enable a disabled segment in memory map UI

[emesare]

The memory map has a way to disable segments, but once a user does that, there is no way to enable said view from the UI.

We should likely show the segment as disabled (i think the best way would be to just have it greyed out?). With the disabled segments you can then show the "Enable segment option".

If the user needs to they can enable the disabled segment using the API for the time being.

https://api.binary.ninja/binaryninja.binaryview-module.html#binaryninja.binaryview.MemoryMap.set_memory_region_enabled

Considering this a bug because UI actions should where applicable be reversible from the UI.