S7 ojo_tbl class

[brancengregory]

…sing the same api

[andrewjbe]

The current issues I see:

• Need to get ojo_collect() working with ojo_tbl(..., source = "arrow") <- mostly done now
• Need to fix text failures
  • ojo_list_vars() test is failing -- when run in non-interactive mode, inherits(ojo_list_vars(...), "tbl_Pool") returns FALSE instead of the expected TRUE
  • ojo_list_tables() test is failing -- looks like it's just complaining about changes to the db schemas, and just needs to have the snapshots updated
  • ojo_tbl() test is failing -- snapshot result of ojo_tbl("case", .con = db) has changed; might just need to update the snapshot, but I'm not 100% sure.

[andrewjbe]

I also think we should ideally lock down the GCS and add some kind of authentication to this