BUG#26985561: BACKPORT BUG#26277771 TO 5.7 - BUG#27016053: REGRESSION IN BINLOG_LOG_ROW INTRODUCED BY ADD_PKE

This is backport of
Bug#26277771: BAD WRITE SET TRACKING WITH UNIQUE KEY ON A
DELETE FOLLOWED BY AN INSERT, which includes the optimizations
present on BUG#27016053: REGRESSION IN BINLOG_LOG_ROW INTRODUCED BY
ADD_PKE.

Issue:
======
The Writesets generated for keys were not using collation into consideration,
and because of that wrong last_committed and sequence_number were
getting added to binary log and thus transactions were getting applied
in wrong order by parallel applier on slave.

Solution:
=========
The fix uses make_sort_key to transform keys, with different charset and
collation, into its binary image, suitable for sorting using binary
comparison.

Optimizations:
==============
During detailed performance analysis it was discovered that there
were non-optimized memory allocations and memory copy operations on
the write-set extraction.

In order to solve the performance regression, the following actions
were made:
 1) optimize memory allocation;
 2) reduce memory copy operations;
 3) only collect foreign key write-sets when them are not disabled;
 4) do not collect and send duplicate write-sets through the network.