[GR-69732] More natural Java subclassing in Python. Github #470.

[graalvmbot]

This test now works. Seems much nicer UX

import java
java.add_to_classpath(".")
MiscUtils = java.type("MiscUtils")

class Misc(MiscUtils, old_style=False):
    def __init__(self):
        print(f"Misc.__init__ runs to initialize the object {self=}")
        self.misc_value = 42

    def numIntsNeededToStoreBytes(self, byteCount):
        print(f"== Misc(MiscUtils).numIntsNeededToStoreBytes({byteCount=}) overrides a Java method, so calls to the Java object go here")
        return self.getClass().static.numIntsNeededToStoreBytes(byteCount)

    def py_native_test_bit(self, val, bit):
        return val & (1 << bit)

    def py_call_numIntsNeededToStoreBytes(self, byteCount):
        print(f"  -->   inside py_call_numIntsNeededToStoreBytes, which is not callable from Java at all")
        _ = self.misc_value
        y = self.numIntsNeededToStoreBytes(10)
        x = self.py_native_test_bit(y if y else 7, 1)
        return y if x else None

misc = Misc()

print(f"{misc.mask(10)=}")
print(f"{misc.py_call_numIntsNeededToStoreBytes(10)=}")
print(f"{misc.py_native_test_bit(7, 1)=}")
print(f"{misc.extractBits(7, 1, 2)=}")
print(f"{misc.misc_value=}")
print(f"{misc.someInstanceMethod()=}")
print(f"{Misc=}")
print(f"{misc=}")
print(f"{type(misc)=}")
print(f"{type(misc).mro()=}")
print(f"{issubclass(Misc, MiscUtils)=}")
print(f"{issubclass(Misc, Misc)=}")
print(f"{isinstance(Misc(), MiscUtils)=}")
print(f"{isinstance(Misc(), Misc)=}")

public abstract class MiscUtils {

    public String someInstanceMethod() {
        return "an instance method on the Java side";
    }

    public static int mask(int v) {
        return v;
    }

    public static int numIntsNeededToStoreBytes(int byteCount) {
        return (byteCount + 3) / 4;
    }

    public static long extractBits(long from, int lsb, int width) {
        return (from >>> lsb) & mask(width);
    }
}