userspace: adjust arch memory domain interface

The current API was assuming too much, in that it expected that
arch-specific memory domain configuration is only maintained
in some global area, and updates to domains that are not currently
active have no effect.

This was true when all memory domain state was tracked in page
tables or MPU registers, but no longer works when arch-specific
memory management information is stored in thread-specific areas.

This is needed for: #13441 #13074 #15135

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>