memblock tests: Add memblock_remove tests

memblock tests: Add memblock_remove tests

Add checks for removing a region from available memory in different
scenarios:
 - The requested region matches one in the collection of available
   memory regions
 - The requested region does not exist in memblock.memory
 - The region overlaps with one of the entries: from the top (its end
   address is bigger than the base of the existing region) or from the
   bottom (its base address is smaller than the end address of one of
   the regions)
 - The region is within an already defined region

Signed-off-by: Karolina Drobnik <karolinadrobnik@gmail.com>
Signed-off-by: Mike Rapoport <rppt@kernel.org>
Link: https://lore.kernel.org/r/8e6aa005407bbe1a75b75e85ac04ebb51318a52a.1643796665.git.karolinadrobnik@gmail.com