feat: added support for IPv6

[CosmicPangolin]

@kevmoo Tagging you here 'cause I figure this repo doesn't get a lot of attention. This is a trivial patch that I needed to unlock some functionalities on the Fly.io subnet, which relies heavily on IPv6 for internal resolution and load balancing. Doubt it conflicts with any GCP needs?

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[kevmoo]

I think the convention on cloud run is to use IPv4 still.

I wonder if we'll have to just add a configuration option or something...

[CosmicPangolin]

My understanding is that the IPv6 option covers IPv4 addresses as well (this could be documented better in the dart:io api, methinks).

[kevmoo]

My understanding is that the IPv6 option covers IPv4 addresses as well (this could be documented better in the dart:io api, methinks).

It's the opposite. All ipV4 addresses are v6, but not the other way around!

[CosmicPangolin]

Agreed :) I just mean InternetAddress.anyIPv6 resolves both, wrt cloud run requiring v4.

[kevmoo]

it seems like tests still pass!

Would you add a changelog entry here!