This includes:
- cleanup and optimization of filtering and pushdown engine code.
- Adjusted costs for rowid filters (based on extensive testing
  and profiling).

This made a small two changes to the handler_rowid_filter_is_active()
API:
- One should not call it with a zero pointer!
- One does not need to call handler_rowid_filter_is_active() for every
  row anymore. It is enough to check if filter is active by calling it
  call it during index_init() or when handler::rowid_filter_changed()
  is called

The changes was to avoid unnecessary function calls and checks if
pushdown conditions and rowid_filter is not used.

Updated costs for rowid_filter_lookup() to be closer to reality.
The old cost was based only on rowid_compare_cost. This is now
changed to take into account the overhead in checking the rowid.

Changed the Range_rowid_filter class to use DYNAMIC_ARRAY directly
instead of Dynamic_array<>. This was done to be able to use the new
append_dynamic() functions which gives a notable speed improvment
compared to the old code.  Removing the abstraction also makes
the code easier to understand.

The cost of filtering is now slightly lower than before, which
is reflected in some test cases that is now using rowid filters.