In my merge of the MySQL fix for Oracle Bug#23333990 / WL#9513
I overlooked some subsequent revisions to the test, and I also
failed to notice that the test is actually always failing.

Oracle introduced the parameter innodb_stats_include_delete_marked
but failed to consistently take it into account in FOREIGN KEY
constraints that involve CASCADE or SET NULL.

When innodb_stats_include_delete_marked=ON, obviously the purge of
delete-marked records should update the statistics as well.

One more omission was that statistics were never updated on ROLLBACK.
We are fixing that as well, properly taking into account the
parameter innodb_stats_include_delete_marked.

dict_stats_analyze_index_level(): Simplify an expression.
(Using the ternary operator with a constant operand is unnecessary
obfuscation.)

page_scan_method_t: Revert the change done by Oracle. Instead,
examine srv_stats_include_delete_marked directly where it is needed.

dict_stats_update_if_needed(): Renamed from
row_update_statistics_if_needed().

row_update_for_mysql_using_upd_graph(): Assert that the table statistics
are initialized, as guaranteed by ha_innobase::open(). Update the
statistics in a consistent way, both for FOREIGN KEY triggers and
for the main table. If FOREIGN KEY constraints exist, do not dereference
a freed pointer, but cache the proper value of node->is_delete so that
it matches prebuilt->table.

row_purge_record_func(): Update statistics if
innodb_stats_include_delete_marked=ON.

row_undo_ins(): Update statistics (on ROLLBACK of a fresh INSERT).
This is independent of the parameter; the record is not delete-marked.

row_undo_mod(): Update statistics on the ROLLBACK of updating key columns,
or (if innodb_stats_include_delete_marked=OFF) updating delete-marks.

innodb.innodb_stats_persistent: Renamed and extended from
innodb.innodb_stats_del_mark. Reduced the unnecessarily large dataset
from 262,144 to 32 rows. Test both values of the configuration
parameter innodb_stats_include_delete_marked.
Test that purge is updating the statistics.

innodb_fts.innodb_fts_multiple_index: Adjust the result. The test
is performing a ROLLBACK of an INSERT, which now affects the statistics.

include/wait_all_purged.inc: Moved from innodb.innodb_truncate_debug
to its own file.