Allow Consul Service Mesh to be used with custom CNI bridges

### Proposal

Nomad has a hard-coded requirement on [`network_mode` `bridge` for service mesh applications](https://github.com/hashicorp/nomad/blob/v1.5.0/nomad/job_endpoint_hook_connect.go#L549-L551) and [`network_mode` `bridge` or `host` for service mesh gateways](https://github.com/hashicorp/nomad/blob/v1.5.0/nomad/job_endpoint_hook_connect.go#L585-L588). This prevents Consul Service Mesh from being used with custom CNI networks. While not all CNI may work with Consul Service mesh Nomad should be more lenient on how this is validated.

### Use-cases

Use Consul Service mesh with custom CNI networks.

### Attempted Solutions

N/A

> **Note**
> Issue extracted from https://github.com/hashicorp/nomad/issues/13824. Refer to that issue for more context.

Start in nomad/job_endpoint_hook_connect.go at the service mesh application and gateway network_mode validation linked in the issue. Trace how these checks are applied to custom CNI networks and review the context in issue #13824. Done means valid Consul Service Mesh jobs using custom CNI networks are not rejected solely by the hard-coded network mode requirement.

Written by the indexing model from the issue text.