Use a safer mechanism for freezing intrinsics

[kriszyp]

The issue is most easily described with:

$ node --use-strict
> Object.freeze(Object.prototype)
[Object: null prototype] {}
> let o = {}
undefined
> o.toString = () => 'hi'
Uncaught TypeError: Cannot assign to read only property 'toString' of object '#<Object>'

Note that this code is not attempting to modify Object.prototype, it is simply performing a very reasonable assignment of the toString property on a plain object. But it throws an error because it "inherits" the read-only-ness of the property slot. And this causes a lot of problems for 3rd party packages.

This fix defines commonly assigned properties with an overridable version of the method that uses a setter to properly allow the value to be set on the derivative object, and then freezing, allowing the property assignment to work properly. I verified that next.js can indeed load properly with this environment freeze in place.

Also note that with this lockdown as the default, the isolation unit tests are running with this freeze in place and testing it.