ospf: Add RFC 9339 support

[nrybowski]

This PR adds the support for Reverse Metric and Reverse TE Metric advertisement through the LLS data block of Hello packets, as defined by RFC 9339.

It depends on RFC 5613 whose support has been added with #77.

TODO

• Add Reverse (TE) Metric LLS TLVs encoding / decoding
  • Add encoding / decoding tests for OSPFv2
  • Add encoding / decoding tests for OSPFv3
• Enable reverse metric configuration
  • Add YANG model. (There is no YANG model specific to OSPF for now, I will adapt the one for IS-IS.)
  • Extend northbound interface
    • Directly send Hello packet upon Reverse (TE) Metric enabling / disabling
  • Extend OSPF configuration to store Reverse (TE) Metric configuration
• Implement Reverse Metric logic
  • Trigger Router LSA origination upon Reverse Metric reception

[rwestphal]

Add YANG model. (There is no YANG model specific to OSPF for now, I will adapt the one for IS-IS.)

Indeed. I see there's [email protected] but no equivalent module for OSPF.

There's draft-ietf-lsr-ospf-yang-augmentation-v1, which adds several augmenting modules to ietf-ospf. We can add our own holo-ospf-reverse-metric and potentially ask the IETF folks to integrate it into that draft. That would probably be welcome on their part, especially since it would come with a working implementation.