Arch docs: motivate/explain custom product image

[nightkr]

Should summarize how and why our upstream images diverge from upstream/3rd party Docker images, as well as mention that upstream images are generally not compatible.

These are the current divergences for Trino vs upstream AFAIK (should probably be generalized so that the list applies to the whole platform):

• we use RedHat UBI8 (for now), they use UBI9
• they publish one image per Trino version, we only maintain images for select Trino versions but maintain them for the lifetime of the Stackable SDP release
• we bundle plugins for JMX monitoring, Trino Storage, and OPA (for Trino versions without native support)
• we include extra tools like Kerberos
• we use RHEL Java, they use Adoptium Java
• our filesystem layouts are different, so our operators expect the layout produced by our images

Originally asked on Discord: https://discord.com/channels/796665978481803304/796665978481803307/1221898284545605713

non-trino specific things:

• standardizing things across the platform (paths, build system, base distro, etc)
• LTS maintenance for specific product versions
• SDP-specific patches (for example: to play nicer with secret-op/list-op)

[fhennig]

I have started a page about this here: #605

You wanna have a look?