Remove support for neutron lbaas in favor of Octavia

[nikParasyr]

Currently most lbaas data-sources/resources work for both neutron lbaas AND octavia. This leads to:

• the code being more complicated "than it should"
• new features from octavia cannot be introduced easily and quickly

Neutron lbaas has been deprecated since Queens(2018-02-28) and removed in Train(2019-10-16). We also dont have ci coverage for it for 2+ years.

The provider aims to support all versions of Openstack and it doesn't have an official deprecation policy. That being said, since it is blocking us from adding new features AND it has been removed for 4 years, I am in favor of removing support for neutron lbaas from the provider.

Would like to hear more opinions on this and if anyone is still using neutron lbaas.

---

Update 29/01: New release was made with deprecation warning for all lbaas resources. Will start working on removing support for neutron lbaas and prep 2.0.0

Resources needing update:

• [x] l7 policy
• [ ] l7 rule
• [ ] listener
• [ ] loadbalancer
• [ ] members
• [ ] member
• [ ] monitor
• [ ] pool
• [ ] quota
• [ ] various help functions, ci scripts and provider "use-octavia" attribute

[yomovh]

I agree that the provider shall fully support Octavia. If that means breaking some features from neutron lbaas then I can live with that.

[nikParasyr]

new release: https://github.com/terraform-provider-openstack/terraform-provider-openstack/releases/tag/v1.54.0 has marked the various resources as deprecated with a relevant message. Will slowly work into updating each resource