Cleanup iptables rules for other CNI networks

### Proposal

https://github.com/hashicorp/nomad/pull/15407 introduced a mechanism to monitor and clean-up iptables rules created by Nomad. The code uses a [regular expression](https://github.com/hashicorp/nomad/blob/v1.5.0/client/allocrunner/networking_cni.go#L252-L254) to find rules managed by Nomad, but it hardcodes `"name: \\"nomad\\"` where `nomad` is the default name that Nomad uses for its built-in bridge. Users that have custom CNI bridges will have different names that would not match this expression and therefore may leak.

### Use-cases

Run a custom bridge using CNI plugins.

### Attempted Solutions

N/A

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

Start in client/allocrunner/networking_cni.go around lines 252-254 and inspect how the regular expression identifies Nomad-managed iptables rules. Trace how custom CNI bridge names are represented, then verify that cleanup also matches rules for those bridges without losing the existing built-in bridge behavior.

Written by the indexing model from the issue text.