[RPC] Prevent use of FinalizationRegistry for workers support

[Dexus]

FinalizationRegistry is not on all systems available, while it works in the most browsers, serverless worker will not supported.

Cloudflare don't support it, same on other Cloud Providers.

[pi0]

@anonrig Do you think workerd would eventually support FinalizationRegistry?

(update: made it conditional: 0b91ec4)

[anonrig]

@anonrig Do you think workerd would eventually support FinalizationRegistry?

(update: made it conditional: 0b91ec4)

Cc @jasnell

[jasnell]

Unlikely. For a number of reasons workers do not allow GC to be observed. It's not something we're likely to add.