refactor: IR support for resolving multi-scope queries (#48)

Refactored a lot of the IR + helper functions to support multiple
scopes.

A table is represented properly with TableRef to ensure correct name
resolution, and the column is uniquely identified by (table_index,
column_index).

We also now convert to the DataFusion logical plan instead of the
ExecutionPlan. The next step is to use a user-defined node to add
implementation hints. This feels a more maintainable integration
compared to directly converting it into a physical plan.

---------

Signed-off-by: Yuchen Liang <yuchenl3@andrew.cmu.edu>

Author: yliang412

Cargo.lock

@@ -4,15 +4,13 @@ members = [
     "cli",
     "connectors/datafusion",
     "optd/core",
-    "optd/catalog",
     "synopses",
     "tests/sqllogictest",
     "tests/sqlplannertest",
 ]
 
 default-members = [
     "optd/core",
-    "optd/catalog",
     "connectors/datafusion",
     "synopses",
     "tests/sqllogictest",