SNOW-782235: Support multi table INSERT clause (`INSERT ALL`)

[sjhewitt]

What is the current behavior?

There is currently no support

What is the desired behavior?

Add an InsertAll clause, similar to MergeInto, etc

How would this improve snowflake-connector-python?

more compatibility with snowflake db features

References, Other Background

https://docs.snowflake.com/en/sql-reference/sql/insert-multi-table

[sfc-gh-dszmolka]

hi and thank you for raising this, especially for the contribution, much appreciated! I requested review from the connector team on it, hopefully it can be picked up soon