Implementing partitioning natively in InnoDB, so it does not need
ha_partition generic partition engine for supporting partitioning.

ha_partition uses one ha_innobase handler for each partition which
does not share common data with each other resulting in high resource
usage which this WL fix.

It also makes it easier to support other InnoDB features that partitioning
currently does not support.

A new handler ha_innopart is added, inheriting both ha_innobase (for InnoDB
access) and Partition_helper (for partitioning support, see wl#4807).

And to avoid a proxy object for Partition_handler (see wl#4807) it is also
inherited.

Also ha_partition is changed to inherit Partition_handler directly.

As a result of this there is no longer any need for .par files
for partitioned InnoDB tables, since InnoDB can use its internal
data dictionary for finding partitions during rename and delete.

The optimizer estimate is also changed, especially for
records_in_range, where all used partitions are checked instead
of only the biggest ones.

rb#7636
Approved by Krunal and Annamalai