fix(cli): simplify Metro watch mode and communicate when disabled

[byCedric]

Why

Fixes ENG-7089

How

Because this option is only exposed through Metro.runServer, I added the override in @expo/cli. Alternative, we could add a custom Metro config option to move this to the config itself, however, that would create a significant diversion of the normal Metro config.

Note
We could add a Metro version check and disable the warning, but I think it's safe to skip that and leave it in for older Metro versions. It's not really synced, but if the message pops up, it's very very likely Metro actually is running without watch.

Test Plan

See added tests.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).

[linear]

ENG-7089 Override Metro's watch option

• feat: expose watch option facebook/metro#889
• Metro disables HMR too aggressively, we should just check if $CI is defined, then log that HMR is disabled due to the CI env var. This will work nicer than the opaque ci-info check.
• https://twitter.com/albingroen/status/1610374540772741121?s=46&t=17itJjueSeSkXeZG31LOGA

[EvanBacon]

LGTM, just need changelog