Fix calculation of non-free region count.

Calculation of number of non-free region also included
region allocations for evacuation. This could have lead
to premature denial of region allocations to mutators.

Definition of FreeLarge() function has been moved to -inl.h file.

Bug: 70732633
Test: make test-art-host
Change-Id: I98e29ca94b101254ef33cf8bca1dd71c93bb253d