Replaces the use of SWC parser in the Forget fixture tests with Hermes Parser.
This includes aligning on a single type to represent JS Values and numbers
(combining semi-duplicated code from forget_hir and forget_estree) and adding
support for lowering babel-style
NumericLiteral/BooleanLiteral/StringLiteral/NullLiteral node types (since Hermes
Parser produces a mix of estree/babel node types)