Snowddl

- Added `NETWORK_POLICY` and `RESOURCE_MONITOR` to list of supported object types.

- Added `is_sandbox` for `DATABASE` object type, in addition to `SCHEMA` object type.
- Dump empty `params.yaml` files for `DATABASE` and `SCHEMA` during conversion to preserve empty schemas. Empty directories cannot be pushed to Git.
- Added basic safety checks for `env_prefix`. It cannot contain double underscore `__` and it cannot end with underscore `_`.

- Added optional `-r` (ROLE) and `-w` (WAREHOUSE) arguments for SnowDDL CLI interface.
- Added basic converters from existing `DATABASE`, `SCHEMA`, `TABLE`, `SEQUENCE` objects to SnowDDL YAML configs.
- Removed future grants from `SCHEMA ROLE (WRITE)` for `VIEW` object type.
- "Getting Started Test" workflow now runs each config version twice to detect possible changes being missed on first run.
- Fixed bug with `comment` and `default` not being applied to `TABLE` columns in some cases.
- Fixed bug with short hashes being used as byte-strings instead of properly decoded pure `ascii` representations.
- Fixed bug with other alters being applied to columns dropped from `TABLE` in some cases.
- Fixed bug with table column comment not being applied immediately on `ADD COLUMN`.
- Fixed bug with role comment not being applied immediately on `CREATE ROLE`.
- Reworked the way how `comment` is being applied to `VIEW` object type. Snowflake implicitly modifies view `text` in `SHOW VIEWS` if it contains a `comment` during `CREATE VIEW`, which breaks view checks on subsequent runs.
- If `VIEW` was replaced, the resolve result is now `REPLACE` instead of `ALTER`.

- Fixed typing annotations for `List` and `Dict` to make it compatible with Python 3.7.

- SnowDDL was released under an open source license.