schema: wrong validation of cc_users_groups

This bug was originally filed in Launchpad as [LP: #1979491](https://bugs.launchpad.net/cloud-init/+bug/1979491)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2022-06-22T09:54:20.224282+00:00

date_fix_committed = None

date_fix_released = None

id = 1979491

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1979491

milestone = None

owner = aciba

owner_name = Alberto Contreras

private = False

status = triaged

submitter = aciba

submitter_name = Alberto Contreras

tags = []

duplicates = []

_Launchpad user **Alberto Contreras(aciba)** wrote on 2022-06-22T09:54:20.224282+00:00_

The schema validation does detect the following wrong schema as valid:

```yaml
#cloud-config
groups:
- 3.14
```

Steps to reproduce:

```sh
cat < /tmp/user-data
#cloud-config
groups:
- 3.14
EOF

lxc launch ubuntu-daily:jammy gg --config=user.user-data="$(cat /tmp/user-data)"
$ lxc exec gg -- cloud-init status --wait
..............
status: error

$ lxc exec gg -- grep -ni "error" /var/log/cloud-init.log
412: raise TypeError(
413:TypeError: Unknown group name type float
440: raise TypeError(
441:TypeError: Unknown group name type float

$ lxc exec gg -- cloud-init schema --system
Valid cloud-config: system userdata

$ lxc exec gg -- echo $?
0
```

The schema validation should detect this schema as invalid.