fix: keep the property name when shimming a shorthand property

[dsherret]

Closes #329

An object literal shorthand property whose name is a shimmed global emitted invalid code. For example, this:

export const _internals = {
  prompt,
};

...emitted this to src/:

export const _internals = {
  dntShim.prompt,
};

...which the compiler then silently emitted as { dntShim, : .prompt, } in the output. Now the property name is kept:

export const _internals = {
  prompt: dntShim.prompt,
};

This applies to the globalThis and window replacements as well ({ window } was becoming { globalThis }, which quietly renamed the property).

Only a shorthand property is affected — a computed key, spread, or explicit key that happens to use a shimmed global still resolves the way it did before.