Feature: IOS-XR experimental support

[garymccann]

Adds: #348

What's Changed

This feature PR adds support for the Cisco IOS-XR network operating system, allowing Nautobot operators to add IOS-XR devices.

To Do

IOS-XR does not operate a VLAN database in the way IOS, IOS-XE or NXOS does. As such, there is no current support for VLANs in this feature. That is not to say that IOS-XR does not utilise 802.1Q tags. These are present in sub-interfaces and under L2VPN functionality. This feature may be revisited in the future.

This feature does not take Etherchannel into account, known as Bundles in IOS-XR. This feature may be revisited in the future

• Explanation of Change(s)
• Added change log fragment(s) (for more information see the documentation)
• Attached Screenshots, Payload Example
• Unit, Integration Tests
• Documentation Updates (when adding/changing features)
• Outline Remaining Work, Constraints from Design

[garymccann]

NOTE: Do not Merge until networktocode/ntc-templates#2092 has been merged and the pyproject updated to reflect the production code (currently points to my personal branch)

[jeffkala]

NOTE: Do not Merge until networktocode/ntc-templates#2092 has been merged and the pyproject updated to reflect the production code (currently points to my personal branch)

This is merged but need to wait on the release and pyproject pinning

[jeffkala]

NOTE: Do not Merge until networktocode/ntc-templates#2092 has been merged and the pyproject updated to reflect the production code (currently points to my personal branch)

This is merged but need to wait on the release and pyproject pinning

ntc-templates is released now: https://github.com/networktocode/ntc-templates/releases/tag/v7.9.0

We should be able to rebase this PR, update pin of ntc-templates and get this merged.