qemu-iotests: 300: Add test case for modifying persistence of bitmap

Verify that the modification of the bitmap persistence over migration
which is controlled via BitmapMigrationBitmapAliasTransform works
properly.

Based on TestCrossAliasMigration

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <d9c8e9827e9b6001b2dd1b92e64aab858e6d2a86.1613150869.git.pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: Adjust test for explicit read_zeroes=False]
Signed-off-by: Eric Blake <eblake@redhat.com>