Add cloudflare internal symbol to resourcetypes

[jasnell]

Miniflare has been using the lack of Symbol.toStringTag to detect internal API objects. This is brittle and problematic because for compliance with standard web platform APIs we're supposed to be adding the Symbol.toStringTag to standard types and there are modules in the ecosystem that depend on it. We recently landed a change that adds the Symbol.toStringTag to types but that broke miniflare. This PR adds an alternative symbol to jsg::Objects that can identify themselves as internal.

[petebacondarwin]

LGTM

[mrbbot]

Could you use the existing kResourceTypeInspect symbol for this?

workerd/src/workerd/jsg/resource.h

Line 920 in b45d297

auto symbol = v8::Symbol::ForApi(isolate, v8StrIntern(isolate, "kResourceTypeInspect"_kj));

workerd/src/node/internal/internal_inspect.ts

Line 1101 in b45d297

internal.kResourceTypeInspect

[jasnell]

Could you use the existing kResourceTypeInspect for this?

Possibly but I think for the sake of time since we need this to unblock something for release tomorrow this is better. Keep in mind that kResourceTypeInspect uses a private ForApi Symbol so the user (miniflare tests in this case) would need to have some way of importing that from somewhere and currently the only way to do that is with nodejs compat on, which complicates things a bit. This uses the global Symbol.for(...) registry to make importing it unnecessary. For now, let's keep it like this and if we can reconcile and simplify the two later then awesome.