Support manipulating the RWX permission of a memory region

[xusheng6]

Now that #memory region is supported, we should allow changing the permissions on them. Apparently not all adapters would support them, but it is a nice addition for those do. Also -- page permissions are usually managed at page level, so we might need to decide if we want to support manipulating page permissions as well

[xusheng6]

Add it should be added to the context menu of the memory map widget