Rename a few lexer and parser infrastructure classes/interfaces

* Rename `AntlrAdapter` &rarr; `SimpleAntlrAdapter`, to clarify that this implementation only works with "simple" ANTLR lexers, i.e. lexers that do not require tracking of custom state information.
* Rename `AbstractAntlrAdapter` &rarr; `AntlrAdapter` for consistency with other IntelliJ lexer adapter classes.
* Rename `ASTElementFactory` &rarr; `PsiElementFactory`, since it is used to create instances of `PsiElement`.