Snowddl

- Added explicit notice when `CREATE OR REPLACE TABLE` is about to drop a column from table.
- It is now possible to set `is_sandbox: false` on schema level when `is_sandbox: true` on database level.
- Fixed ENV variable name `SNOWFLAKE_ROLE`.

- Added missing conversion logic for `DatabaseBlueprint` when operating in SingleDB mode. It no longer prevents schemas from being dropped in this mode.

- Added `ICEBERG_TABLE` object type to make it available for grants and permission models.

- Added parameters `owner_database_read`, `owner_database_write` to `DATABASE` config. It only works if both current database and target database has permission model with `database_owner` ruleset.

- Fixed issue with ACCOUNT-level policy references.

- Introduced CLI option `--env-prefix-separator` which allows to choose separator for env prefix from one of three pre-defined variants: `__`, `_`, `$`. Default is `__`.
- Implemented `AUTHENTICATION_POLICY` object type. It can be referenced from `ACCOUNT_POLICY` and `USER` configs.
- Reworked `WAREHOUSE` resolver, implemented `resource_constraint` parameter for Snowpark-optimized warehouses.