Remove the old type encoding.

After weeks of switching everything over to the typed ASTs, we have
finally reached the point where we can completely remove the old type
encoding based on ValueLinearizers and JDBC-related accessor methods in
Column classes.

- Only one reference to the lifted embedding remaining in the query
  compiler (CreateResultSetMapping matches on Column).
- No remaining references to the lifted embedding in the AST and the
  direct embedding.
- No remaining references to JDBC in the AST and the query compiler
  (still some work to do for separating the embeddings into different
  profiles).