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.
Erik Marks