fix: Item.equal now compares components on 1.20.5+

[AnonymoDGH]

Problem

Since 1.20.5, item data (custom name, damage, enchantments, lore, repair cost, ...) is stored in components/componentMap instead of NBT. But Item.equal only compares type, metadata, count and nbt — so two items that differ only in their components are reported as equal.

Reproduction (1.20.5):

const a = Item.fromNotch({ itemId: swordId, itemCount: 1, components: [{ type: 'custom_name', data: 'Excalibur' }] })
const b = Item.fromNotch({ itemId: swordId, itemCount: 1, components: [] })
Item.equal(a, b) // true  <- wrong, should be false

Same for damage, enchantments, and removedComponents differences.

This is the root cause behind PrismarineJS/mineflayer#3933: mineflayer's inventory.js gates updateSlot on Item.equal (if (!Item.equal(bot.inventory.slots[slot], item, true)) bot.inventory.updateSlot(slot, item)), so on 1.20.5+ component changes (renames, damage, enchants) are silently dropped and items fail to synchronize.

Fix

Add a componentsEqual helper that compares componentMap entries (by type and serialized data) and removedComponents, and evaluate it inside Item.equal under the existing matchNbt flag — components are the 1.20.5+ replacement for NBT item data, so they belong to the same "match item data" semantics.

• Pre-1.20.5 items have no componentMap and are completely unaffected (helper returns true immediately).
• matchNbt=false skips component comparison, consistent with skipping NBT.
• No signature change; fully backward compatible.

Verification

• New regression tests cover: different custom_name, different damage, different enchantments, identical components, different removedComponents, and matchNbt=false.
• Full suite: 114 passing (108 existing + 6 new), standard lint clean.