DDL survival: VTMD tracking

Added:

• VTMD tables are created as copy of mysql.vtmd_template;
• VTMD tracking: CREATE, ALTER, DROP, RENAME;
• Versioned SHOW CREATE TABLE as tracked by VTMD;
• Additional clauses for GENERATED AS ROW fields: NOT NULL, [PRIMARY] KEY, UNIQUE [KEY], COMMENT.

Fixed:

• IB: start_time_micro usage;
• CREATE TABLE .. LIKE;
• ALTER TABLE .. ADD COLUMN.