SWP Policy Rule - Mitigate multiple rules issue

[modular-magician]

Hello folks.

This PR is to mitigate the issue when creating and/or deleting multiple google_network_security_gateway_security_policy_rule

• When creating multiple rules at the same time it can throw an internal error which looks like a race condition.
• When deleting multiple rules and the policy, the rules delay a little bit to propagate, causing an issue on the policy that can't be destroyed which looks like there is a phantom rule on the policy.

Release Note Template for Downstream PRs (will be copied)

See Write release notes for guidance.

networksecurity: added wait time on `google_network_security_gateway_security_policy_rule` resource when creating and deleting to prevent race conditions

Derived from GoogleCloudPlatform/magic-modules#12704