Configure FRR containers with Linux scripts

[ipspace]

This commit implements Ansible-free configuration of FRR containers. Unfortunately, the trivial implementation (devices.frr.clab.config_mode, add shebang to config templates) would break custom config templates, so we had to go for a more complex solution:

• Add 'netlab_config_wrapper' group variable -- a Jinja2 template that is used as a generic post-processing phase for device configs
• Use that wrapper deep in the bowels of templating code to generate valid scripts out of existing FRR configuration templates

Further FRR changes:

• The 'netlab_mgmt_vrf' variable is not changed based on the presence of the VRF module; the 'can we use VRFs' test is moved into the initial configuration bash script.
• FRR daemons need a bit of time to start, but it's hard to figure out when exactly they're ready. As a hack, "sleep 1" command (specified in netlab_config_exec) is added to clab.exec list by the clab provider whenever the netlab_config_mode is set

Other changes:

• clab.config_templates is enforced to be a dict
• Timing of a few integration tests had to be tweaked because FRR is configured earlier/faster than before

[Copilot]

Pull request overview

This PR implements Ansible-free configuration for FRR containers using shell scripts executed by containerlab. The implementation introduces a netlab_config_wrapper mechanism to transform FRR configuration templates into executable shell scripts, and moves VRF module availability checks from configuration-time to runtime.

Changes:

• Introduced netlab_config_wrapper group variable for post-processing device configurations with a Jinja2 template
• Modified FRR container configuration to use runtime checks for VRF kernel module availability
• Enforced clab.config_templates to be a dict type for consistency
• Added sleep 1 exec command to FRR containers to allow daemons to start before configuration
• Adjusted integration test wait times for BGP AF activation due to faster container startup

Reviewed changes

Copilot reviewed 14 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
netsim/utils/templates.py	Added render_wrapper function to apply config wrappers and integrated it into write_template
netsim/providers/clab.py	Simplified config mode logic to use get_node_group_var and added exec command handling
netsim/providers/clab.yml	Changed config_templates attribute type from untyped to dict
netsim/devices/frr.yml	Added config wrapper template, config mode, and exec command for FRR containers
netsim/ansible/templates/initial/frr.j2	Changed VRF management logic to runtime checks instead of configuration-time checks
netsim/ansible/templates/vlan/frr.j2	Added set -x for command tracking during troubleshooting
tests/integration/wait_times.yml	Added bgp_af_activate wait time of 5 seconds
tests/integration/evpn/13-vxlan-ebgp-allowas.yml	Added wait times for BGP AF activation checks
tests/integration/bgp/20-dual-stack-activate.yml	Added wait times for BGP AF activation checks
tests/topology/input/clab-attributes.yml	Updated test to disable config mode and use dict for config_templates
tests/topology/expected/*.yml	Updated test expectations to reflect new config structure with scripts, binds, and exec commands