adjust parser for IOSXE 'show running-config aaa username' to be less rigid

[thepurplebuffalo]

Description

This change adjusts how the IOSXE parser for show running-config aaa username works.

Motivation and Context

I recently encountered a problem where this username line was skipped by the parser:

username testuser8 privilege 15 common-criteria-policy Test-CC secret 9 <hash>

The existing regular expressions (8 of them) each match entire username lines that meet a specific format. The line above did not match any of those expressions. The result was that the username was silently skipped by the parser. None of the 8 existing regular expressions allow for both privilege and common-criteria-policy on the same line.

I have changed the general nature of this parser to treat the username line like a stack. Arguments are popped off of the beginning of the line (along with their parameters) so that the arguments can exist in flexible combinations.

This code is untested as the project Makefile relies on resources internal to Cisco.

Impact (If any)

Screenshots:

None.

Checklist:

• I have updated the changelog.
• I have updated the documentation (If applicable).
• I have added tests to cover my changes (If applicable).
• All new and existing tests passed.
• All new code passed compilation.