This PR makes ~all named intrinsics in all of our JavaScript processes non-modifiable. A named intrinsic is any property specified by the ECMAScript specification that exists on `globalThis` when the JavaScript process starts. We say that a property is non-modifiable if it is non-configurable and non-writable. We make exceptions for properties that meet any of the following criteria:
1. Properties that are non-configurable by the time `lockdown-run.js` is executed are not modified, because they can't be.
2. Properties that have accessor properties (`get` or `set`) are made non-configurable, but their writability cannot be modified, and is therefore left unchanged. It's unclear how many of the named intrinsics this applies to, if any, but it's good defensive programming, regardless.
