[Java.Interop.Tools.JavaCallableWrappers] [Export]+params

[jonpryor]

Fixes: dotnet/android#7554

Placing [Export] on a constructor with parameters did not work as expected. Consider:

public class Example : Java.Lang.Object
{
    [Export(SuperArgumentsString = "")]
    public Example (int value)
    {
        this.value = value;
    }

    int value;
}

This does generate a Java Callable Wrapper with the desired constructor, but it doesn't invoke the correct C# constructor, because of the TypeManager.Activate() invocation:

// Java JCW
/* partial */ class Example extends java.lang.Object {
    public Example(int p0) {
        super ();
        if (getClass () == Example.class) {
            mono.android.TypeManager.Activate (
                    /* typeName */      "Namespace.Example, Assembly",
                    /* signature */     "",
                    /* instance */      this,
                    /* parameterList */ new java.lang.Object[] { p0 });
        }
    }
}

In particular, because signature is the empty string, TypeManager.Activate() will lookup and invoke the default constructor, rather than the Example(int) constructor. (This despite the fact that parameterList contains arguments!)

Consequently, when Java invokes the Example(int) constructor, an exception is thrown, as the default constructor it wants doesn't exist:

Could not activate JNI Handle 0x7ffd2bd94e50 (key_handle 0x65d856e) of Java type 'namespace/Example' as managed type 'Namespace.Example'.
Java.Interop.JavaLocationException: Exception of type 'Java.Interop.JavaLocationException' was thrown.
Java.Lang.Error: Exception of type 'Java.Lang.Error' was thrown.

  --- End of managed Java.Lang.Error stack trace ---
java.lang.Error: Java callstack:
	at mono.android.TypeManager.n_activate(Native Method)
	at mono.android.TypeManager.Activate(TypeManager.java:7)
	at namespace.Example.<init>(Example.java:0)
	…

Update JavaCallableWrapperGenerator.AddConstructor() so that the managedParameters value is provided to the Signature instance for the [Export] constructor. This value is then inserted as the signature parameter value, which will allow the correct constructor to be invoked:

// Fixed Java JCW
/* partial */ class Example extends java.lang.Object {
    public Example(int p0) {
        super ();
        if (getClass () == Example.class) {
            mono.android.TypeManager.Activate (
                    /* typeName */      "Namespace.Example, Assembly",
                    /* signature */     "System.Int32, System.Runtime",
                    /* instance */      this,
                    /* parameterList */ new java.lang.Object[] { p0 });
        }
    }
}