feat(substrait): add extension table consumer hook

[kadinrabo]

Custom consumers can already override consume_read, but handling only ReadRel::ExtensionTable means copying the rest of from_read_rel.

This adds the same narrow hook used for extension relation cases. It doesn't add producer support or default table serialization.

Part of #13771

Tested with cargo test -p datafusion-substrait

[vbarua]

One bit of API that might be worth thinking about if you haven't already.

The NamedTable and LocalFiles read_types call the read_with_schema function at the end to also translate the projection, and filter fields of the ReadRel message. read_with_schema assumes that the translated read_type is vaguely TableReference shaped

With the addition of ExtensionTable, we have two read_types that aren't TableReference shaped (the other is VirtualTable) and don't correctly handle the projection and filter fields. Now might be a good time to try and figure out a better abstraction to handle those fields consistently for all read types.