Gentler handling of removed directives and commands (omit_containers, --mutagen-enabled, --use-traefik)

[gilbertsoft]

Expected Behavior

People expect old commands and directives to still work in v1.22.0:

• omit_containers[dba] shouldn't create an error even if it's ignored. (project only, could give a message about deprecation)
• --mutagen-enabled (global and project) could just set performance_mode: mutagen, maybe explain deprecated
• --nfs-mount-enabled (global and project)
• --use-traefik (global) can make sure that router: traefik

There may be a couple other things we should handle more gracefully

Actual Behavior

When using these currently users get errorrs.

ddev config --auto
You are reconfiguring the project at /home/simon/development/GsActions/commit-message-checker.
The existing configuration will be updated and replaced.
Configuring unrecognized codebase as project of type 'php' at /home/simon/development/GsActions/commit-message-checker
failed to validate config: unsupported omit_containers: [db dba ddev-ssh-agent], ddev (amd64) only supports the following for omit_containers: [db ddev-ssh-agent]

or

ddev start
Failed to get project(s): unsupported omit_containers: [db dba ddev-ssh-agent], ddev (amd64) only supports the following for omit_containers: [db ddev-ssh-agent]

Steps To Reproduce

No response

Anything else?

No response

[rfay]

I wonder if we could just accept dba but remove it after loading.