feat: Add Server TLS Policy parameter

[bnounours]

Hello,

In my infra we put in place mTLS authentication on the load balancer. For that we declared a google_certificate_manager_trust_config and a google_network_security_server_tls_policy. To make the link I added server_tls_policy to module and used it in google_compute_target_https_proxy

Thanks to this modification I now have a Load Balancer SSL with mTLS

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[imrannayer]

@bnounours thx for the PR. Can you plz follow the document and make this change in autogen.

Thanks

[bnounours]

Hello,
I launched the make build to generate the doc and the modules => Ok
I launched the make docker_test_lint => Ok but do not generate anything so we don't see it in the repo.
I did not luanch make docker_test_prepare as I don't have the right in my company to create project and set billing account

[imrannayer]

/gcbrun