Add support for Google manages certificates

Official docs describes API for creating Google Managed certificates (via Let's Encrypt??):

https://cloud.google.com/load-balancing/docs/ssl-certificates/google-managed-certs
https://cloud.google.com/sdk/gcloud/reference/compute/ssl-certificates/create
https://cloud.google.com/sdk/gcloud/reference/compute/ssl-certificates

Existing module `google.cloud.gcp_compute_ssl_certificate` allows only to import pre-existed certificate: https://docs.ansible.com/ansible/latest/collections/google/cloud/gcp_compute_ssl_certificate_module.html

Start with the existing google.cloud.gcp_compute_ssl_certificate module and the linked Google Cloud certificate creation documentation. Compare the module's current import-only behavior with the documented Google Managed certificate API and gcloud options. Done means the module can create Google Managed certificates with suitable parameters and preserves existing certificate support.

Written by the indexing model from the issue text.