Allow disabling IPv6 for emulators (e.g. for Codespaces port forwarding)

Environment info

firebase-tools: 9.16.6

Platform: Linux

Test case

Install firebase-tools.

Steps to reproduce

Run the firebase emulators with npx firebase emulators:start

Expected behavior

All services would bind to 127.0.0.1 (and, optionally, also to [::ffff:127.0.0.1]). The codespaces port forwarding feature would work as expected.

Actual behavior

Some services (in particular the firestore emulator) only bind to IPV6 localhost:

State      Recv-Q     Send-Q              Local Address:Port          Peer Address:Port    Process                               
LISTEN   0        4096       [::ffff:127.0.0.1]:43299                  *:*       users:(("java",pid=19991,fd=78))                                               
LISTEN   0        4096       [::ffff:127.0.0.1]:8080                   *:*       users:(("java",pid=19991,fd=79))                                               
LISTEN   0        50         [::ffff:127.0.0.1]:36567                  *:*       users:(("java",pid=19991,fd=22))                                               
LISTEN   0        4096       [::ffff:127.0.0.1]:34265                  *:*       users:(("java",pid=19991,fd=53))                                               

and the codespaces port forwarding is not working.

[bkendall]

@markgoho we have a function that does check for that variable specifically isCloudEnvironment: https://github.com/firebase/firebase-tools/blob/master/src/utils.ts#L554-L559

(not sure how it’s used throughout the codebase, but that seems like a good exercise for the reader 🙂 )

[bkendall]

v11.14.3 has better logic in it that should help with not binding to ipv6 if it’s unavailable. Give that a whirl (without overriding all the things) and see if that helps?