[Relay] Add ADTs to text format (#3863)

* Getting closer to having ADT defs

* ADT defs working probly

* Match parsing basipally done

* came to earth in a silver chrome UFO

* match finished?

* All tests but newest are passing

* ADT constructors work

now cleanup?

* Cleanup round 1

* Cleanup round 2

* Cleanup round 3

* Cleanup round 4

* Cleanup round 6

* Cleanup round 7

* Lil grammar fix

* Remove ANTLR Java files

* Lint roller

* Lint roller

* Address feedback

* Test completeness in match test

* Remove unused imports

* Lint roller

* Switch to Rust-style ADT syntax

* Lil fix

* Add dummy `extern type` handler

* Add type arg to test

* Update prelude semantic version

* Repair test

* Fix graph var handling in match

* Revert 's/graph_equal/is_unifiable' change

Author: weberlo

include/tvm/relay/adt.h

@@ -264,7 +264,7 @@ class MatchNode : public ExprNode {
   /*! \brief The match node clauses. */
   tvm::Array<Clause> clauses;
 
-  /*! \brief Should this match be complete (cover all cases)? 
+  /*! \brief Should this match be complete (cover all cases)?
    *  If yes, the type checker will generate an error if there are any missing cases.
    */
   bool complete;

include/tvm/relay/module.h

@@ -164,6 +164,13 @@ class ModuleNode : public RelayNode {
    */
   TVM_DLL TypeData LookupDef(const std::string& var) const;
 
+  /*!
+   * \brief Check if a global type definition exists
+   * \param var The name of the global type definition.
+   * \return Whether the definition exists.
+   */
+  TVM_DLL bool HasDef(const std::string& var) const;
+
   /*!
    * \brief Look up a constructor by its tag.
    * \param tag The tag for the constructor.