R4R: Uint overhaul

[alessio]

• Safe implementation:
  • Ops return values are guaranteed greater-than-or-equal-0.
  • Constructors fail if supplied input is < 0.
• Remove dead code (e.g. NewUintWithDecimal, unused).
• Comprehensive test suite.

This work is done in preparation for migrating away from Int once and for all.

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added entries in PENDING.md with issue #
• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #3665 into develop will decrease coverage by 0.63%.
The diff coverage is 90%.

@@             Coverage Diff             @@
##           develop    #3665      +/-   ##
===========================================
- Coverage    61.22%   60.58%   -0.64%     
===========================================
  Files          189      190       +1     
  Lines        14039    14191     +152     
===========================================
+ Hits          8595     8598       +3     
- Misses        4902     5054     +152     
+ Partials       542      539       -3

[jleni]

The 030303 issue hit you :|