Remove [[ExecutionContext]]

[leobalter]

cc @syg @caridy @rwaldron

[littledan]

This patch looks like a correct way to implement @syg's suggestion, but I don't understand the motivation for the change. Stashing an execution context is a sort of common technique to make it easier to get into a Realm, e.g., also found in HTML's environment settings objects.

[leobalter]

My only goal is unblock all the way to Stage 4, so I don't have a strong preference for this PR or otherwise.

Somehow this proposed approach makes importValue a bit closer to Realm#evaluate.

I'm also pretty confident we're going to eventually rename the GetNewRealmContext.

[leobalter]

Pinging @syg as I want to make sure this address his feedback.

[leobalter]

PR rebased with conflicts resolved.

[leobalter]

pinging the @tc39/ecma262-editors here. This PR has no observable changes, but matches a request from @syg on the Stage 3 review. I'd like to confirm this is the desired direction for the eventual PR to ECMA-262.

[rwaldron]

This makes sense.

[caridy]

@ptomato is this ready for review? what is the latest here?

[ptomato]

@caridy I rebased it the other day, but I don't know the context of the original request, so maybe @leobalter or @syg should have a look before merging it.

[caridy]

maybe @nicolo-ribaudo has opinions about this change.