[vm/compiler] Use unchecked entry point when static receiver type is non-generic.

This guarantees that type checks are skipped in the code like this:

class X<T> {
  void method(X<T> other) {
  }
}

class Y extends X<String> {
}

void foo(Y y, Y z) {
  y.method(z);  // No need to check on the callee side. No variance.
}

Additionally ammend IL printing to print user visible type names instead
of internal type names for brevity.

Bug: https://github.com/dart-lang/sdk/issues/31798
Change-Id: I4fe16d5dc7de01bb0a8ba834569d90ee5ce7ac74
Reviewed-on: https://dart-review.googlesource.com/72001
Reviewed-by: Samir Jindel <sjindel@google.com>
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>