cleanup(test): Make test debugging output more readable

[teor2345]

Motivation

Sometimes Zebra produces 30,000 lines of debug output from a single test:
https://github.com/ZcashFoundation/zebra/actions/runs/5321638950/jobs/9636992835?pr=7019#step:10:4911

Some Zebra structs have debug impls which print arrays of u8, rather than hex-encoded strings.

Solution

Hide the extremely long debug output.

Manually implement the debug impls to use hex encoded strings.

Review

This is a low priority cleanup.

Reviewer Checklist

• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

[codecov]

Codecov Report

Merging #7027 (f0fcbc2) into main (b40fc9b) will increase coverage by 0.04%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7027      +/-   ##
==========================================
+ Coverage   77.39%   77.44%   +0.04%     
==========================================
  Files         310      310              
  Lines       41635    41669      +34     
==========================================
+ Hits        32224    32270      +46     
+ Misses       9411     9399      -12     

[oxarbitrage]

nice one, looks good to me.