Update parser for Snowflake stage metadata

[osipovartem]

Summary

• update the Embucket SQL parser revision to include Snowflake SHOW STAGES
• expose the dedicated DESC[RIBE] STAGE AST statement to downstream consumers

Dependency-only update; no DataFusion execution behavior changes.

Validation

• cargo check -p datafusion-sql --locked
• cargo test -p datafusion-sql --lib --locked
• cargo fmt --check
• git diff --check

Parser PR: Embucket/datafusion-sqlparser-rs#33