:wrench: Upgrade Ruby / Alpine / KEA

[Gary-H9]

This PR updates the following:

• ruby:3.0.3-alpine3.13 -> ruby:3.1.2-alpine3.14
• Ruby 3.0.3 -> 3.1.2
• Alpine 3.13 -> 3.14
• KEA 2.0 -> KEA 2.2

Such a substantial number of upgrades are required since we do not build from source i.e. we are reliant on the images available online, and associated repositories which are available for each version of Alpine. More detail below.

Why are you upgrading KEA?

The upgrade to KEA is required as when building with ruby:3.1.2-alpine3.14 and KEA 2.0 the following errors occur during build:

...
#5 18.31     required by: world[isc-kea-admin]
#5 18.31   isc-kea-ctrl-agent (no such package):
#5 18.31     required by: world[isc-kea-ctrl-agent]
#5 18.31   isc-kea-dhcp4 (no such package):
#5 18.31     required by: world[isc-kea-dhcp4]
#5 18.31   isc-kea-hook-ha (no such package):
#5 18.31     required by: world[isc-kea-hook-ha]
#5 18.31   isc-kea-hook-lease-cmds (no such package):
#5 18.31     required by: world[isc-kea-hook-lease-cmds]
#5 18.31   isc-kea-hook-stat-cmds (no such package):
#5 18.31     required by: world[isc-kea-hook-stat-cmds]
#5 18.31   isc-kea-perfdhcp (no such package):
#5 18.31     required by: world[isc-kea-perfdhcp]
...

This is because KEA 2.0 is not available in the Alpine 3.14 image.
KEA 2.2 is however available in the Alpine 3.14 image.

The changes above encapsulate the minimum number of changes we can make to upgrade the Alpine image.

Prior to merging we need to:

• ~further understand occasional (~80%) failures in testing leases~
• understand any changes which may be needed as a result of upgrading Ruby - read the release notes between 3.0.3 and 3.1.2
• understand any changes which may be needed as a result of upgrading KEA - release notes and previous commits around June/July

[Gary-H9]

Tested in Dev and Pre-Prod, containers load fine and there are no errors of note in the startup. We have also tested loading new config by editing a site in Pre-Prod and watching the container reload it.