expectedType in proof-printing code (#3665)

expectedType in proof-printing code (#3665)

* expectedType in proof-printing code

To print lemma proofs in theories that use multiple sorts that have a
subtype relationship, we need to increase communication between the
TheoryProofEngine and the theory proofs themselves.

This commit add an (optional) argument `expectedType` to many
term-printing functions in TheoryProofEngine and TheoryProof.

Right now it is unused, so always takes on the default value of "null"
(meaning no type expectation), but in the future the TheoryProofEngine
will use it to signal TheoryProof about what type is expected to be
printed.

* TypeNode, Don't mix default args & virtual

* Use TypeNode instead of Type (The former are lighter)
* Don't add default arguments to virtual functions, because these cannot
  be dynamically overriden during a dynamic dispatch.
  * Since we don't want them to be overidable anyway, we use two
    functions: one that is non-virtual and has a default, the other that
    is virtual but has no default. The former just calls the latter.

* clang-format after signature changes