`gcp_compute_route` requires `dest_range` with `state: absent`

##### SUMMARY

When setting `state: absent` in `gcp_compute_route`, the module complains that `dest_range` is not set. The same happens with `gcp_compute_subnetwork` and the `ip_cidr_range` parameter.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME

gcp_compute_route

##### COLLECTION VERSION

```paste below
google.cloud 1.1.2
```

Latest master actually.

Original discussion [here](https://github.com/ansible/ansible/issues/56325).

Possible solution:

Instead of:

https://github.com/ansible-collections/google.cloud/blob/226ec3dd3fb2eb3b2131014816240298126400fc/plugins/modules/gcp_compute_route.py#L344-L359

do:

```python
module = GcpModule(
argument_spec=dict(
state=dict(default='present', choices=['present', 'absent'], type='str'),
dest_range=dict(type='str'), # CHANGED
description=dict(type='str'),
name=dict(required=True, type='str'),
network=dict(required=True, type='dict'),
priority=dict(type='int'),
tags=dict(type='list', elements='str'),
next_hop_gateway=dict(type='str'),
next_hop_instance=dict(type='dict'),
next_hop_ip=dict(type='str'),
next_hop_vpn_tunnel=dict(type='dict'),
next_hop_ilb=dict(type='dict'),
),

# CHANGED
required_if=[
(`state`, `present`, (`dest_range`)),
]
)
```

Start in plugins/modules/gcp_compute_route.py at the argument specification around the referenced lines, and compare the state handling with the issue's proposed requirement. Check the corresponding gcp_compute_subnetwork parameter behavior as well. Done means absent state no longer requires dest_range, while present state still validates it.

Written by the indexing model from the issue text.