DebugInfo: Don't simplify any template referencing a lambda

Lambda names aren't entirely canonical (as demonstrated by the
cross-project-test added here) at the moment (we should fix that for a
bunch of reasons) - even if the template referencing them is
non-simplified, other names referencing /that/ template can't be
simplified either because type units might cause a different template to
be picked up that would conflict with the expected name.

(other than for roundtripping precision, it'd be OK to simplify types
that reference types that reference lambdas - but best be consistent
between the roundtrip/verify mode and the actual simplified template
names mode)