Add LDC constant helper methods

[Jonathing]

This PR aims to address the pains of dealing with LDC constant instructions.

• The buildLdcInsnNode() method uses a LdcNumberType to ensure that the exact type of number is fed into the LdcInsnNode constructor. Fixes Would like a way to create LDC with a float value #42.
• The ldcInsnClassToString method gets the class name of the constant stored in the given LdcInsnNode, making it easier to debug existing LDC constant instructions. Fixes No way to check type of LDC? #30.

Will remain as draft until I test these additions myself.

[Jonathing]

I have tested this PR in Forge and it is ready for a proper review. Here's what I used to test this:

CoreMod:

var ASMAPI = Java.type('net.minecraftforge.coremod.api.ASMAPI');
var Opcodes = Java.type('org.objectweb.asm.Opcodes');

function initializeCoreMod() {
    return {
        'thunderHit_ldc_test': {
            'target': {
                'type': 'METHOD',
                'class': 'net.minecraft.world.entity.Entity',
                'methodName': 'thunderHit',
                'methodDesc': '(Lnet/minecraft/server/level/ServerLevel;Lnet/minecraft/world/entity/LightningBolt;)V'
            },
            'transformer': thunderHit
        }
    };
}

function thunderHit(method) {
    ASMAPI.log('INFO', 'HELLO! ENTERING LDC TEST');

    var insn = ASMAPI.findFirstInstruction(method, Opcodes.LDC);

    ASMAPI.log('INFO', 'LDC instruction object class: {}', ASMAPI.ldcInsnClassToString(insn));
    ASMAPI.log('INFO', 'LDC instruction object value: {}', insn.cst);

    ASMAPI.log('INFO', 'SETTING NEW LDC! SETTING VALUE TO 12.0F');

    var newInsn = ASMAPI.buildNumberLdcInsnNode(12.0, ASMAPI.LdcNumberType.FLOAT);
    method.instructions.set(insn, newInsn);

    ASMAPI.log('INFO', 'NEW LDC instruction object class: {}', ASMAPI.ldcInsnClassToString(newInsn));
    ASMAPI.log('INFO', 'NEW LDC instruction object value: {}', newInsn.cst);

    return method;
}

RESULTING LOG MESSAGES:

[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: HELLO! ENTERING LDC TEST
[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: LDC instruction object class: class java.lang.Float
[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: LDC instruction object value: 8.0
[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: SETTING NEW LDC! SETTING VALUE TO 12.0F
[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: NEW LDC instruction object class: class java.lang.Float
[11:03:29] [pool-5-thread-1/INFO] [ne.mi.co.Co.forge/COREMODLOG]: NEW LDC instruction object value: 12.0

This example changes the time set in fire from thunder hit from 8 to 12.