Inspired by #5160

I haven't fixed the issues identified by this query (I got a patch ready, but I wanted to reduce the scope of the PR).

This query identifies two patterns:

1: A redundant aggregate like:

exists(PredicateExpr alias | alias = this.(ClasslessPredicate).getAlias() |
  result = alias.getArity()
)

Can be simplified to:

result = this.(ClasslessPredicate).getAlias().getArity()

2: Aggregates that can be simplified to a type-cast:
exists(Type t | t = foo()) can be simplified to foo() instanceof Type.
(And any(Type t | t = foo()) can be simplified to foo().(Type)).

Note: an exists(..) is actually a qualifier and not an aggregate, but I'm unsure what else to call something that is either an exists(..) or an any(..).