Arista: implement neighbor deletion and add warnings

[dhalperi]

1. Implement delete neighbor for IPv4 neighbors.
2. Add warnings around improper deletions.

[batfish-bot]

This change is 

[ratulm]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @dhalperi)

[codecov]

Codecov Report

Merging #8260 (ea2f882) into master (1ce37e4) will decrease coverage by 0.00%.
The diff coverage is 55.26%.

@@             Coverage Diff              @@
##             master    #8260      +/-   ##
============================================
- Coverage     74.57%   74.56%   -0.01%     
- Complexity    43735    43743       +8     
============================================
  Files          3405     3406       +1     
  Lines        169415   169451      +36     
  Branches      20233    20240       +7     
============================================
+ Hits         126340   126357      +17     
- Misses        33502    33522      +20     
+ Partials       9573     9572       -1     

Impacted Files	Coverage Δ
...representation/arista/eos/AristaBgpV6Neighbor.java	0.00% <0.00%> (ø)
...sh/grammar/arista/AristaControlPlaneExtractor.java	47.57% <77.77%> (+0.16%)	⬆️
...bddreachability/BDDReachabilityGraphOptimizer.java	82.82% <0.00%> (-1.02%)	⬇️
...ain/java/org/batfish/storage/FileBasedStorage.java	85.47% <0.00%> (-0.62%)	⬇️
...batfish/src/main/java/org/batfish/main/Driver.java	49.18% <0.00%> (-0.55%)	⬇️
...java/org/batfish/dataplane/ibdp/VirtualRouter.java	87.56% <0.00%> (-0.25%)	⬇️
...tfish/representation/cisco/CiscoConfiguration.java	84.71% <0.00%> (-0.15%)	⬇️
...src/main/java/org/batfish/coordinator/WorkMgr.java	75.81% <0.00%> (+0.31%)	⬆️
...ain/java/org/batfish/coordinator/WorkQueueMgr.java	71.51% <0.00%> (+0.58%)	⬆️
... and 2 more