Revert InferUnion change in new-ast

[f37yu]

The partially unresolved inferred parameters are actually useful as suggested by test results. In new-ast an optimization caused this to be no longer possible.
The previous change silenced errors in this case and dropped all unresolved inferred parameters, assuming those alternatives are always eliminated. Unfortunately, this does not always happen, so the memory optimization makes resolver incorrect.

Affected code:
ResolvExpr::InferMatcher? at SatisfyAssertions?.cpp:226
Expr::InferUnion? at Expr.hpp:68
Old implementation:
ResolvExpr::InferMatcher? at ResolveAssertions?.cc:327