feat: add support for host and path rules in URL map

[bwmacedo]

Issue #466
This PR introduces support for host and path rules within the terraform-google-lb-http module, enhancing its flexibility for routing configurations. It adds two new variables, host_rules and path_matchers, to allow users to define custom host-based and path-based routing rules in URL maps. This change enables more granular control over HTTP(S) load balancing behavior, particularly for use cases involving Serverless NEGs (e.g., Cloud Run, App Engine).

Changes:

New Variables:

• host_rules: Defines host rules, associating specified hosts with a path matcher.
• path_matchers: Allows detailed path matching configurations, including path rules and default services.

URL Map Resource Update:

• Updated the google_compute_url_map resource to support dynamic host_rule and path_matcher blocks based on the new variables. This enhancement provides modular and flexible routing options for complex load balancer setups.

Example Configuration:

host_rules = [
  {
    hosts        = ["example.com"]
    path_matcher = "example-path-matcher"
  }
]

path_matchers = [
  {
    name            = "example-path-matcher"
    default_service = google_compute_backend_service.default.self_link
    path_rules = [
      {
        paths   = ["/path1", "/path2"]
        service = google_compute_backend_service.other_service.self_link
      }
    ]
  }
]

Motivation:
This enhancement reduces the need for module customization, making it easier to configure complex load balancing scenarios directly within the module. This is especially beneficial for users with requirements for specific host and path routing logic.

Additional Information:
Documentation updates and additional examples are included to illustrate usage scenarios.

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