pre_start containers don't inherit/support extra_hosts

[hberntsen]

Description

Hi, thanks for the awesome pre_start feature!

We're running into the problem that we 're not seeing extra_hosts in the pre_start containers being applied. For example:

services:
  test:
    image: busybox
    extra_hosts:
      - "somehost:162.242.195.82"
    pre_start:
      - command: cat /etc/hosts
    command: cat /etc/hosts

Then, running docker compose up outputs:

laughing_hertz  | 127.0.0.1	localhost
laughing_hertz  | ::1	localhost ip6-localhost ip6-loopback
laughing_hertz  | fe00::	ip6-localnet
laughing_hertz  | ff00::	ip6-mcastprefix
laughing_hertz  | ff02::1	ip6-allnodes
laughing_hertz  | ff02::2	ip6-allrouters
laughing_hertz  | 172.19.0.2	731eafcc9089
laughing_hertz exited with code 0
test-1          | 127.0.0.1	localhost
test-1          | ::1	localhost ip6-localhost ip6-loopback
test-1          | fe00::	ip6-localnet
test-1          | ff00::	ip6-mcastprefix
test-1          | ff02::1	ip6-allnodes
test-1          | ff02::2	ip6-allrouters
test-1          | 162.242.195.82	somehost
test-1          | 172.19.0.2	876dcd9db560
test-1 exited with code 0

The somehost is not visible in the laughing_hertz pre_start container.