Snowflake: parse sequence lifecycle commands

[osipovartem]

Summary

• parse Snowflake CREATE [OR REPLACE | OR ALTER] SEQUENCE options
• add ALTER, SHOW, and DESCRIBE SEQUENCE AST support
• preserve the existing PostgreSQL-compatible CREATE SEQUENCE option path
• cover lifecycle syntax, filtering, comments, modifiers, and invalid forms

Snowflake references:

• https://docs.snowflake.com/en/sql-reference/sql/create-sequence
• https://docs.snowflake.com/en/sql-reference/sql/alter-sequence
• https://docs.snowflake.com/en/sql-reference/sql/show-sequences
• https://docs.snowflake.com/en/sql-reference/sql/desc-sequence

Validation

• cargo +1.95.0 test --all-features
• cargo +1.95.0 clippy --all-targets --all-features -- -D warnings
• cargo +1.95.0 fmt --all -- --check
• git diff --check

Live Snowflake probes were used to verify option spelling, metadata shape, idempotency, and the one-way ORDER to NOORDER transition.