WL#8434: True bottom-up server parser: refactoring of partitioning-related stuff

This WL is a part of umbrella refactoring WL#6707 "Refactor MySQL server parser to build the AST in a natural bottom-up way".

The WL will refactor partitioning-related parts of the grammar:

• partitioning clauses of CREATE/ALTER TABLE statements,
• PARTITION pseudo-SQL statement (data definition in .frm).

See requirements at the umbrella WL#8067 page.

See specifications at the umbrella WL#8067 page.

See specifications at the umbrella WL#8067 page.