Operators
- Create operator enums to wrap internal Jorje operators.
- Create getters returning new operator enums in operator-expression
  nodes. Deprecate old getters.
- Refactor metrics classes to use new operator enums.

Tests
- Remove references to internal Jorje nodes.

- Replace `ApexNode` type arguments with `Void`
- Remove `ApexNode.getNode`
- Remove `ASTCommentContainer` type parameter
- Deprecate `ASTUserClassOrInterface` type parameter

Remove `node` field from `AbstractApexNode` to remove restriction of
wrapping a single node. Create `AbstractApexNode.Single` subclass that
wraps a single node.

Other subclasses can be created as needed for common cases, or
`AbstractApexNode` can be extended directly in irregular cases.

- Add call to `SummitAST` in `ApexParser`
- Fix NPE involving `suppressMap` to allow `ApexTreeBuilder` to run
- Remove unused `TopLevelVisitor`

Replace `CompilationUnit` with `TypeDeclaration` as the top-level node
to match the AST produced by Jorje.

- Replace `ApexTreeBuilder.java` with `ApexTreeBuilder.kt`
- Set up tree builder foundation
- Build `TypeDeclaration` nodes

- Add `AbstractApexNode.Many`

- Add `buildChildren` function to tree builder

- Split `setParent` call from main `build` function into new
  `buildAndSetParent`
- Remove list-based `build` function to decrease complexity
- Improve documentation

- Remove Jorje dependencies
- Add Summit-AST dependency
- Comment out code until compilation succeeds

- Replace `ApexNode` type arguments with `Void`
- Remove `ApexNode.getNode`
- Remove `ASTCommentContainer` type parameter
- Deprecate `ASTUserClassOrInterface` type parameter

Remove `node` field from `AbstractApexNode` to remove restriction of
wrapping a single node. Create `AbstractApexNode.Single` subclass that
wraps a single node.

Other subclasses can be created as needed for common cases, or
`AbstractApexNode` can be extended directly in irregular cases.

- Add call to `SummitAST` in `ApexParser`
- Fix NPE involving `suppressMap` to allow `ApexTreeBuilder` to run
- Remove unused `TopLevelVisitor`

Replace `CompilationUnit` with `TypeDeclaration` as the top-level node
to match the AST produced by Jorje.

- Replace `ApexTreeBuilder.java` with `ApexTreeBuilder.kt`
- Set up tree builder foundation
- Build `TypeDeclaration` nodes

- Add `AbstractApexNode.Many`

- Add `buildChildren` function to tree builder

* Build expression statements
** Build assignment expressions
** Build array expressions
** Build literal expressions
** Build cast expressions
** Build operator expressions
** Build `this`/`super` expressions
** Build type reference expressions
** Build field/variable expressions
** Build method call expressions

* Build ternary expressions
* Refactor `AbstractApexNode`
** Add default implementations for some methods
** Add empty constructor
** Implement `AbstractApexNode.getDefiningType`

* Fix `ASTLiteralExpression.getImage`

* Implement reference types
** Implement `ASTReferenceExpression.isSObjectType`
** Implement `ASTReferenceExpression.hasRealLoc`
** Fix `ASTEmptyReferenceExpression.getDefiningType`

* Implement `ASTMethodCallExpression.getFullMethodName`

* Update `ASTLiteralExpression.getImage`

* Replace `Triple` with `data class`

* Fix `BITWISE_XOR`

* Replace `Identifier.asCodeString` with `getString`

* Fix call expressions
** Only the `receiver` of `CallExpression`s should be flattened

* Fix `referenceTypeOf`
Reference type should only be `STORE` when the variable is the target of
assignment.

* Rename `ASTMethodCallExpression.components`

… part-1

Change-Id: I254208dd5d1b9dbf5335a59a51372ec1d55f8535

…IfPrimitive

These are helper methods to be used only inside the ast package.

…ER_METHOD_NAME

- removed method getContext() - always returned null
  Fixes TODO(b/243906211)
- Verify that getReferenceType() returns the correct values
  Fixes TODO(b/239648780)

Fixes TODO(b/239648780)

This was testing a deprecated XPath attribute,
but that attribute was already removed.

Fixes TODO(b/243905954)

Update release notes/migration guide

Refs google/summit-ast#47