SNOW-751046: get_columns is very slow in schemas with many tables

[thegreymatter]

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when calling get_column for a table, the rationale behind it was an "optimization" that was implemented to load eagerly and cache all columns in the schema when first calling get_column for any table in the schema. while it is a good optimization for smaller schemas, it slows down the experience considerably in larger schemas.

it woudl be great if at the least I will have the ability to override this default behavior.

[sfc-gh-dszmolka]

solution could possibly relate to https://github.com/snowflakedb/snowflake-sqlalchemy/issues/406