Assert class signatures are correct and refer to valid classes

Code in java lang invoke uses strings for explicit class signatures, for example in InvokerBytecodeGenerator.java:

    /**
     * Generate an invoker method for the passed {@link LambdaForm}.
     */
    private byte[] generateCustomizedCodeBytes() {
        classFilePrologue();

        // Suppress this method in backtraces displayed to the user.
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Hidden;", true);

        // Mark this method as a compiled LambdaForm
        mv.visitAnnotation("Ljava/lang/invoke/LambdaForm$Compiled;", true);

        if (lambdaForm.forceInline) {
            // Force inlining of this invoker method.
            mv.visitAnnotation("Ljava/lang/invoke/ForceInline;", true);
        } else {
            mv.visitAnnotation("Ljava/lang/invoke/DontInline;", true);
        }

It would be better to express as constants, that are possibly derived from the actual class (or at least equality-based assertions performed on the string to that derived from the class).

Any such work should ideally wait until JDK-8144223 is integrated into the appropriate repo, since that updates some class signatures (e.g. some of those in the above code snippet)