@MonotonicNonNull and @Nullable fields now prevent final-class constructors from using a method reference at the end

[cpovirk]

This is like #610 but:

• for both @MonotonicNonNull and @Nullable [edit: I actually don't remember for sure whether I checked if @MonotonicNonNull fields now prevent final-class constructors from calling a method at the end #610 affected both]
• for method references instead of method invocations

I see it with 3.39.0-eisop1 and with 3.40.0-eisop2 but not with 3.40.0-eisop2, so I assume that it's part of the general initialization-checker restructuring.

$ cat I2.java 
import org.checkerframework.checker.nullness.qual.Nullable;

final class I2 {
  @Nullable String s;

  I2() {
    use(this::init);
  }

  void init() {}

  static void use(Runnable r) {}
}

$ checker/bin/javac -processor nullness I2.java
I2.java:7: error: [methodref.receiver.bound.invalid] Incompatible receiver type
    use(this::init);
        ^
  found   : @UnderInitialization I2
  required: @Initialized I2
  Consequence: method
    @UnderInitialization I2
  is not a valid method reference for method in @UnderInitialization I2
    void init(@Initialized I2 this)
1 error