About-to-be-revoked blob URLs in workers and in dynamic import

[andreubotella]

Issue #11817 dealt with the case where a Request constructed from a blob URL which was subsequently revoked was supposed to fetch successfully – because URL records in the spec have a "blob URL entry" field that gets populated with the corresponding blob when the URL is parsed, and that blob is used when fetching.

As I pointed out in #11817 (comment), Deno still has this problem for blob URLs when creating workers and in dynamic imports – in the spec, the URL parsing happens synchronously when new Worker(blobUrl) or import(blobUrl) is called, and the blob URL entry gets used during fetching.