Support Snowflake lambda functions

[jmhain]

Snowflake recently gained support for higher-order functions like TRANSFORM and FILTER which utilize a new lambda function syntax similar to that of Databricks for which I recently added support.

The two syntaxes look compatible so we can mostly reuse what we have. The one difference I noted is that Snowflake lambdas are permitted to specify types, e.g. (x INT, y INT) -> (x + y).