General strategy for specifying <database>.<schema>.<table_name> in LazyTbl

[machow]

SQL databases differ in the number of levels in a database. E.g.

• postgres: you connect to a database, can specify a .<table_name>
• snowflake: you can specify all three - ..<table_name>
• bigquery: to my knowledge is similar to snowflake, but the sqlalchemy implementation has funny behavior around the schema piece (which bigquery calls datasets. But to be sure, also calls schemas in rare parts of the docs).

Currently, LazyTbl just does a simple str.split("."), that expects 2 components. Let's figure out a general way to let users specify as many levels as the database and underlying sqlalchemy dialect allow.

Note, as an alternative, siuba could bake this in somehow to the dialects. (but I would rather lean on the dialect implementation if possible).