Analyzer treats tear-off of a constant constructor as not a constant

[sgrekhov]

The following code works well in CFE but fails in analyzer

class C {
  const C();
  const C.named();
}

main() {
  const c1 = C.new;    // Analyzer error - Const variables must be initialized with a constant value
  const c2 = C.named;  // Analyzer error - Const variables must be initialized with a constant value
}

Tested on Dart SDK version: 2.15.0-edge.b2b8e59b2863ef02709dfdb750e9ae8e3732389c (be) (Fri Aug 13 01:08:51 2021 +0000) on "windows_x64"

[lrhn]

The constructor doesn't even need to be declared const, any non-instantiated constructor tear-off is constant.