docker v20.10.24 major changes

Older v20.10.17 docker snap is now published in core18/stable channel. It will remain unchanged, and unlikely to receive any future maintainance.

Major Changes:

• snap base upgraded from core18 to core22
• i386 architecture builds dropped
• snapd 2.59.1 or higher is required (currently in beta channel)
• docker versions updated to v20.10.24
• nftables used by default
• compose v2 is now the default and only compose implementation
• deprecated compose v1 removed
• deprecated machine command plugin removed

Currently in candidate channel, and phasing in stable