The pt-online-schema-change tool was not properly handling RENAME COLUMN
syntax (MySQL 8.0+), causing renamed columns to be excluded from the
data copy operation. This resulted in NULL values for renamed columns
after the schema change.
The issue was in the find_renamed_cols() function which only supported
CHANGE COLUMN syntax but not RENAME COLUMN syntax. Added support for
RENAME COLUMN parsing to properly detect column renames and include
them in the common_cols list for data copying.
Fixes: PT-2418
4a9a4bb903