Use common base docker images to share layers across service images

[groldan]

Sharing docker image layers. Check the number of layers for each service:

BEFORE:

TAG=1.4.1 docker compose pull
[+] Pulling 68/25
 ✔ admin 4 layers [⣿⣿⣿⣿]               0B/0B      Pulled   20.4s 
 ✔ config 3 layers [⣿⣿⣿]               0B/0B      Pulled   13.1s 
 ✔ discovery 3 layers [⣿⣿⣿]            0B/0B      Pulled   16.8s 
 ✔ gateway 10 layers [⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿]      0B/0B      Pulled    4.6s 
 ✔ gwc 5 layers [⣿⣿⣿⣿⣿]                0B/0B      Pulled   32.5s 
 ✔ rest 6 layers [⣿⣿⣿⣿⣿⣿]              0B/0B      Pulled   27.3s 
 ✔ wcs 3 layers [⣿⣿⣿]                  0B/0B      Pulled   27.7s 
 ✔ webui 6 layers [⣿⣿⣿⣿⣿⣿]             0B/0B      Pulled   23.1s 
 ✔ wfs 3 layers [⣿⣿⣿]                  0B/0B      Pulled   16.6s 
 ✔ wms 6 layers [⣿⣿⣿⣿⣿⣿]               0B/0B      Pulled   12.7s 
 ✔ wps 4 layers [⣿⣿⣿⣿]                 0B/0B      Pulled   12.8s

AFTER:

TAG=1.5-SNAPSHOT docker compose pull
[+] Pulling 55/33
 ✔ admin 2 layers [⣿⣿]                 0B/0B      Pulled   12.0s 
 ✔ config 2 layers [⣿⣿]                0B/0B      Pulled   12.1s 
 ✔ discovery 12 layers [⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿]  0B/0B      Pulled    5.0s 
 ✔ gateway 2 layers [⣿⣿]               0B/0B      Pulled    7.7s 
 ✔ gwc 3 layers [⣿⣿⣿]                  0B/0B      Pulled   13.5s 
 ✔ rest 3 layers [⣿⣿⣿]                 0B/0B      Pulled   10.1s 
 ✔ wcs 6 layers [⣿⣿⣿⣿⣿⣿]               0B/0B      Pulled   10.0s 
 ✔ webui 3 layers [⣿⣿⣿]                0B/0B      Pulled   10.1s 
 ✔ wfs 2 layers [⣿⣿]                   0B/0B      Pulled   13.8s 
 ✔ wms 3 layers [⣿⣿⣿]                  0B/0B      Pulled   12.9s 
 ✔ wps 2 layers [⣿⣿]                   0B/0B      Pulled   14.7s