test: incorporates tests for short absence proof verification

[staheri14]

Overview

After investigating the current implementation, verified that the nmt library is capable of verifying short absence proofs. This PR contains the necessary tests to demonstrate and test this capability.

In line with #210

Checklist

• [x] New and updated code has appropriate documentation
• [x] New and updated code has new and/or updated testing
• [x] Required CI checks are passing
• [x] Visual proof for any user facing features like CLI or documentation updates
• [x] Linked issues closed with keywords

[codecov[bot]]

Codecov Report

Merging #217 (1e56c61) into master (48b8f96) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #217   +/-   ##
=======================================
  Coverage   93.67%   93.67%           
=======================================
  Files           5        5           
  Lines         601      601           
=======================================
  Hits          563      563           
  Misses         21       21           
  Partials       17       17           

Impacted Files	Coverage Δ
proof.go	88.48% <ø> (ø)