### What problem does this PR solve?
Issue Number: close#61056#66084
Related PR: #None
Problem Summary:
Add create-time Row TTL support with a hidden TTL column for both
source-time and direct-expiration tables. The implementation removes
dynamic ALTER enablement and dedicated full schema-change/backfill
paths, keeps TTL configured only at CREATE TABLE time, and treats TTL as
a post-merge row visibility rule composed with delete sign. Storage
keeps ordinary compaction policy while filtering expired rows during
reads and natural rewrite paths. FE/BE tests and regression cases cover
property validation, hidden column construction, tablet schema
propagation, visibility filtering, partial updates, planning behavior,
and ALTER rejection.
Co-authored-by: 贾敬哲 <jiajingzhe.1350@bytedance.com>