Snowflake: Add CREATE and DROP EXTERNAL VOLUME

[sabir-akhadov-localstack]

Snowflake's external-volume DDL did not parse. Per the review suggestion this PR was split into four; this one now covers only CREATE [OR REPLACE] EXTERNAL VOLUME [IF NOT EXISTS] and DROP EXTERNAL VOLUME (mirroring the merged CREATE/DROP WAREHOUSE, #2388). The follow-ups are ALTER (#2474), DESC (#2472) and SHOW (#2473).

Example that failed before:

CREATE EXTERNAL VOLUME my_vol STORAGE_LOCATIONS = (
    (NAME = 'loc1' STORAGE_PROVIDER = 'S3' STORAGE_BASE_URL = 's3://bucket/path/'));

Each storage location is a parenthesized key-value option list parsed generically into the existing KeyValueOptions, so fields (including the nested ENCRYPTION = (...) list) may appear in any order, matching real Snowflake. Only an empty location is rejected; semantic checks such as the required STORAGE_BASE_URL or duplicate fields are left to the consumer, in line with the parser's permissive stance. The trailing ALLOW_WRITES and COMMENT properties are accepted in either order. DROP EXTERNAL VOLUME reuses the generic Statement::Drop via a new ObjectType::ExternalVolume. All statements round-trip.

See the Snowflake CREATE EXTERNAL VOLUME docs.

[sabir-akhadov-localstack]

Friendly ping on this one when someone has a moment. 🙂

It's been open since early July; CI is green and it's conflict-free against main. It follows the same structure as the recently merged CREATE WAREHOUSE support (#2388), so it should hopefully be a familiar review. Happy to rebase or adjust anything if needed. Thanks!

[LucaCappelletti94]

I suggest you split this into 4 PRs, one for macro type, so it is more likely to be digested a bit more quickly.

[sabir-akhadov-localstack]

Done, thanks for the suggestion! This PR is now scoped down to CREATE + DROP (mirroring the merged CREATE/DROP WAREHOUSE, #2388), and the rest is split out:

• ALTER: Snowflake: Add ALTER EXTERNAL VOLUME #2474 (draft — stacked on this one, since it reuses the storage-location parsing helper)
• DESC[RIBE]: Snowflake: Add DESC[RIBE] EXTERNAL VOLUME #2472
• SHOW: Snowflake: Add SHOW EXTERNAL VOLUMES #2473

[sabir-akhadov-localstack]

Closed in favor of the fresh split PRs: CREATE + DROP is now #2475, alongside ALTER (#2474), DESC (#2472) and SHOW (#2473).