Bug#15923864 : Bug#67718 : INNODB DRASTICALLY UNDER-FILLS PAGES IN CERTAIN CONDITIONS

InnoDB should try to insert to the next page before split the page, if the insert record for split_and_insert is last of the page.

Otherwise, the (reverse) sequential inserts to the middle of the index might cause 1 record per 1 page.

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The previous attempt had the bug and fixed already at this push.

Bug#19045042 : ASSERT MACH_READ_FROM_8()==INDEX->ID RECV_RECOVERY_IS_ON() IS_INSIDE_IBUF()
The new function btr_insert_into_right_sibling() misses to treat ibuf bitmap for the page which the record inserted.

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Approved by Marko in rb#5856