add BYOC tags list/update/replace commands [MILK-337]

[Prime541]

About this change: What it does, why it matters

This change adds the missing avn byoc tags update command that is shown in Aiven's public documentation, but not in Aiven CLI reference.

It reuses the same syntax as service tags commands.

• avn byoc tags list
• avn byoc tags update --add-tag KEY=VALUE --remove-tag KEY
• avn byoc tags replace --tag KEY=VALUE

I have tested it in a locally deployed BYOC.

(all contributors please complete this section, including maintainers)

MILK-337