fix(engine): run derived class field initializers after super()

[simonyang08]

Fixes #948

A user-written derived class constructor that declared instance fields used to throw ReferenceError: Uninitialized this binding because the field-initializer prelude was emitted at the start of the constructor body, before super() had bound this.

class A {}
class B extends A {
  b = 2
  constructor() { super() }
}
new B() // previously: ReferenceError: Uninitialized this binding

Change

For derived classes, the field-initializer prelude is now built as a separate executable stored on the function and invoked from EvaluateSuper after super() has bound this, mirroring how default constructors already behave. Base-class constructors keep the existing prelude-inside-body path because OrdinaryCallBindThis runs before the user body.

The new helper initialize_ecmascript_function_class_field_initializers mirrors initialize_instance_elements (used by default constructors) so future field-init environment changes should apply to both paths.

Regression test

tests/class-field-init-in-derived.js covers the original issue repro, single/multi-field cases, grand-child fields, a base-class no-regression check, and field visibility after super() inside the constructor.

Verification

• cargo build --bin nova_cli --profile dev-fast — clean
• cargo clippy --bin nova_cli --profile dev-fast — 0 warnings
• cargo fmt --check — clean
• Repro script: ReferenceError before the change → completes normally after
• Workspace unit tests: all green (83 passed, 0 failed)
• Full test262 sweep NOT run (submodule not initialized in this environment) — worth running in CI before merge

Scope note

This fix inherently threads new state through the bytecode compiler, VM, executable, and function data structures, so the diff spans 10 files (+233/-30) — larger than a typical focused patch, but it is a single semantic change. The GC mark/sweep handling for the new class_field_initializer_bytecode field is included.

Signed-off-by: simonyang08 ppt5928@gmail.com