This patch is the result of running
run-clang-tidy -fix -header-filter=.* -checks='-*,modernize-use-equals-default' .

Code style changes have been done on top. The result of this change
leads to the following improvements:

1. Binary size reduction.
* For a -DBUILD_CONFIG=mysql_release build, the binary size is reduced by
  ~400kb.
* A raw -DCMAKE_BUILD_TYPE=Release reduces the binary size by ~1.4kb.

2. Compiler can better understand the intent of the code, thus it leads
   to more optimization possibilities. Additionally it enabled detecting
   unused variables that had an empty default constructor but not marked
   so explicitly.

   Particular change required following this patch in sql/opt_range.cc

   result_keys, an unused template class Bitmap now correctly issues
   unused variable warnings.

   Setting Bitmap template class constructor to default allows the compiler
   to identify that there are no side-effects when instantiating the class.
   Previously the compiler could not issue the warning as it assumed Bitmap
   class (being a template) would not be performing a NO-OP for its default
   constructor. This prevented the "unused variable warning".

Part#2: cleanup:

In the part 1 of the fix, DS-MRR implementation would peek into
the JOIN_TAB to get the rowid filter from

  table->reginfo.join_tab->rowid_filter

This doesn't look good from code isolation standpoint (why should a
storage engine assume it is used through a JOIN_TAB?).

Fixed this by storing the 'un-pushed' rowid_filter in the DsMrr_impl
structure. The filter survives across multi_range_read_init() calls.

It is discarded when somebody calls index_end() or rnd_end() and cleans
up the DsMrr_impl.

This patch fixes the following defects/bugs.
1. If BKA[H] algorithm was used to join a table for which the optimizer
had decided to employ a rowid filter the filter actually was not built.
2. The patch for the bug MDEV-21356 that added the code canceling pushing
rowid filter into an engine for the table joined with employment of
BKA[H] and MRR was not quite correct for Innodb engine because this
cancellation was done after InnoDB code had already bound the the pushed
filter to internal InnoDB structures.

Fix partitioning and DS-MRR to work together

- In ha_partition::index_end(): take into account that ha_innobase (and
  other engines using DS-MRR) will have inited=RND when initialized for
  DS-MRR scan.
- In ha_partition::multi_range_read_next(): if the MRR scan is using
  HA_MRR_NO_ASSOCIATION mode, it is not guaranteed that the partition's
  handler will store anything into *range_info.
- In DsMrr_impl::choose_mrr_impl(): ha_partition will inquire partitions
  about how much memory their MRR implementation needs by passing
  *buffer_size=0. DS-MRR code didn't know about this (actually it used
  uint for buffer size calculation and would have an under-flow).
  Returning *buffer_size=0 made ha_partition assume that partitions do
  not need MRR memory and pass the same buffer to each of them.

  Now, this is fixed. If DS-MRR gets *buffer_size=0, it will return
  the amount of buffer space needed, but not more than about
  @@mrr_buffer_size.

* Fix ha_{innobase,maria,myisam}::clone. If ha_partition uses MRR on its
  partitions, and partition use DS-MRR, the code will call handler->clone
  with TABLE (*NOT partition*) name as an argument.
  DS-MRR has no way of knowing the partition name, so the solution was
  to have the ::clone() function for the affected storage engine to ignore
  the name argument and get it elsewhere.

This commit is based on the work of Michal Schorm, rebased on the
earliest MariaDB version.

Th command line used to generate this diff was:

find ./ -type f \
  -exec sed -i -e 's/Foundation, Inc., 59 Temple Place, Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
  -exec sed -i -e 's/Foundation, Inc. 59 Temple Place.* Suite 330, Boston, /Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, /g' {} \; \
  -exec sed -i -e 's/MA.*.....-1307.*USA/MA 02110-1335 USA/g' {} \; \
  -exec sed -i -e 's/Foundation, Inc., 59 Temple/Foundation, Inc., 51 Franklin/g' {} \; \
  -exec sed -i -e 's/Place, Suite 330, Boston, MA.*02111-1307.*USA/Street, Fifth Floor, Boston, MA 02110-1335 USA/g' {} \; \
  -exec sed -i -e 's/MA.*.....-1307/MA 02110-1335/g' {} \;

The XtraDB storage engine was already replaced by InnoDB
and disabled in MariaDB Server 10.2. Let us remove it altogether
to avoid dragging dead code around.

Replace some references to XtraDB with references to InnoDB.

rpl_get_position_info(): Remove.

Remove the mysql-test-run --suite=percona, because it only contains
tests specific to XtraDB, many of which were disabled already in
earlier MariaDB versions.