Fixed SecurityPolicyRule and RegionSecurityPolicyRule resources being unable to manage the policy default rule

[matheusaleixo-cit]

Adds custom code to allow the google_compute_region_security_policy_rule and google_compute_security_policy_rule resources to override the default rule of their respective security policy without the need of a multi-apply import process.

Fixes: https://github.com/hashicorp/terraform-provider-google/issues/15687

Release Note Template for Downstream PRs (will be copied)

compute: fixed unable to create default rule when using `google_compute_region_security_policy_rule` resource

compute: fixed unable to create default rule when using `google_compute_security_policy_rule` resource