fix: after provider.disconnect() is called, Ganache should stop serving requests

[jeffsmale90]

Previously, when provider.disconnect() was called, a lot of the internals of Ganache would be stopped, but just enough was kept alive to serve requests. This could stop consumers from shutting down cleanly.

Now all pending requests, and any new requests will be rejected with a helpful error.

For example, before this change, the following would successfully return the block number:

const provider = Ganache.provider();
await provider.disconnect();
const blockNumber = await provider.send("eth_blockNumber");

But now:

Error: Cannot process request, Ganache is disconnected.

Caveat: any request that has started to process, but not yet complete, may fail with an unexpected error. See #3499 for details.

Fixes #3293

[cds-amal]

Thanks, @jeffsmale90. I spent a moment to marvel at the fix and left some minor nits.

[MicaiahReid]

Cool stuff!

[jeffsmale90]

I've narrowed the scope of this PR as suggested by @davidmurdoch. It now just stops processing requests, and rejects pending tasks.

It makes a "best effort" attempt to resolve in order, but will fail in most cases, because we do not wait for inflight requests to resolve before shutting down the blockchain. See #3499 to cover those changes.

[davidmurdoch]

Just a question and a comment for you!

[davidmurdoch]

⭐⭐⭐⭐⭐

Would review again!