IOSXE: recognize vasi left/right as valid interface prefixes

[progwriter]

Used for cross-vrf nat on IOS XE: https://www.cisco.com/c/en/us/support/docs/ip/network-address-translation-nat/200255-Configure-VRF-Aware-Software-Infrastruct.html

[batfish-bot]

This change is 

[dhalperi]

Reviewed 3 of 3 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[codecov]

Codecov Report

Merging #6375 into master will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #6375      +/-   ##
============================================
- Coverage     73.04%   73.03%   -0.01%     
  Complexity    35167    35167              
============================================
  Files          2815     2815              
  Lines        142679   142698      +19     
  Branches      17158    17168      +10     
============================================
+ Hits         104216   104219       +3     
- Misses        30229    30231       +2     
- Partials       8234     8248      +14     

Impacted Files	Coverage Δ	Complexity Δ
...tfish/representation/cisco/CiscoConfiguration.java	86.03% <100.00%> (+0.01%)	493.00 <0.00> (ø)
...src/main/java/org/batfish/coordinator/PoolMgr.java	54.76% <0.00%> (-4.77%)	13.00% <0.00%> (-2.00%)
...ain/java/org/batfish/coordinator/WorkQueueMgr.java	70.93% <0.00%> (-0.59%)	90.00% <0.00%> (-1.00%)
...a/org/batfish/representation/aws/LoadBalancer.java	82.18% <0.00%> (-0.32%)	70.00% <0.00%> (-1.00%)
...src/main/java/org/batfish/coordinator/WorkMgr.java	75.60% <0.00%> (-0.31%)	245.00% <0.00%> (-1.00%)
...n/java/org/batfish/datamodel/BgpAdvertisement.java	52.63% <0.00%> (+0.02%)	21.00% <0.00%> (+4.00%)
...col/src/main/java/org/batfish/role/InferRoles.java	90.90% <0.00%> (+1.36%)	51.00% <0.00%> (+1.00%)