DRAFT: feat(iosxr): Update XR output parsing to recognize "Previous State" in bgp output

[jamesharr]

Test inclusion requirements

In case the PR contains an enhancement or a new platform/service support, some tests have to be added for the new functionality:

• any fix or enhancement SHOULD include relevant new tests or test updates, if any tests need updating.
• a new platform support MUST include the relevant input files similar to what we have in tests/integration/sqcmds/-input directories, along with the relevant tests in the tests/integration/sqcmds/-samples dir. That list MUST include the all.yml file fully filled out.
• any new service (or table) addition MUST include comments about what network OS are supported (along with version) with this command along with test samples for those platforms and input files in the *-input dir

For additional information about tests, follow this link

Related Issue

Fixes #

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

New Behavior

...

Contrast to Current Behavior

...

Discussion: Benefits and Drawbacks

...

Changes to the Documentation

...

Proposed Release Note Entry

...

Comments

Include additional comments about the this pull request

Double Check

• I have read the comments and followed the CONTRIBUTING.md.
• I have explained my PR according to the information in the comments or in a linked issue.
• My PR source branch is created from the develop branch.
• My PR targets the develop branch.
• All my commits have --signoff applied