fix: remove migrations completely

src/governor/migration.rs

src/governor/mod.rs

src/governor/plan.rs

src/lib.rs

src/rpc/migration.rs

src/rpc/mod.rs

src/storage.rs

src/traft/mod.rs

test/int/test_migration.py

test/int/test_sql.py

test/manual/sql/test_sql_perf.py