Exposing dev server on addresses other than localhost does not work anymore

[fatadel]

STR:

1. Start profiler with FX_PROFILER_HOST=0.0.0.0 yarn start.
2. Get your IP address, eg with ipconfig getifaddr en0.
3. Add your IP address to the list of allowed hosts here.
4. Access the profiler at http://YOUR_IP:4242.

Expected result:
Profiler opens.

Actual result:
Error text with 403 - Forbidden: The host "YOUR_IP" is not allowed.

Regressed in #5589.

Apparently, happens because of the hardcoded host here, but more investigation would be nice.
I've also noticed that the documentation was not updated after migrating to the es-build dev server, see here.

/cc @mstange @canova

┆Issue is synchronized with this Jira Task

[canova]

Yeah, we should fix this one as well.