fix(global-registrator): install the virtual FormData constructor

Problem

Window exposes VeryHappyFormData, which can populate from a virtual form, but GlobalRegistrator.register() does not replace the host FormData. FormData is absent from OVERRIDE_KEYS, so Bun native FormData remains active and silently ignores the virtual form controls.

Reproduction

import { GlobalRegistrator } from "very-happy-dom"

GlobalRegistrator.register()
document.body.innerHTML = `<form><input name="email" value="test@example.com"></form>`
const data = new FormData(document.querySelector("form")!)
console.log(data.get("email")) // null
console.log(new window.FormData(document.querySelector("form")!).get("email")) // test@example.com

Impact

Component tests using the documented global registration appear to submit an empty form. This is especially easy to miss when a test only checks that the submit event fired.

Acceptance

• Registered global FormData is the Window implementation.
• new FormData(virtualForm) includes successful controls.
• unregister() restores the original host constructor rather than deleting it.

Fixed in b947a78, released in v0.1.11.

Verified against the published package rather than the source tree, using the reproduction from the issue:

new FormData(form).get(email) = "test@example.com"
globalThis.FormData === window.FormData = true
FormData.prototype is intact = object

Adding FormData to OVERRIDE_KEYS alone is not the fix — it overflows the stack. The wrapper delegates empty construction to globalThis.FormData, which is itself once registered, so new FormData() recursed until the stack ran out (RangeError: Maximum call stack size exceeded). It now holds the host constructor captured at module load.

A second defect surfaced while satisfying "the registered global FormData is the Window implementation": registration bound every function on its way to globalThis, constructors included. A bound function is a different object and has no prototype, so globalThis.FormData !== window.FormData and FormData.prototype was undefined. That was true of every class the Window exposes — Event, HTMLElement, Document and the rest — not only FormData. Constructors are now copied as they are.

Third acceptance item is done too: unregister() restores what it displaced instead of deleting it, so a host global survives a register/unregister cycle. Deleting had been removing Bun's own constructors outright.

Five tests cover it, including the no-argument construction that would otherwise recurse, and a navigator case proving the restore is general rather than special-cased for FormData. Suite is 1599 passing.