feat: added Abs() funcs, support for overflow for uints + tests

[MalekLahbib]

the files were updated from https://github.com/rwxe/overflow (MIT).
Added Abs functions to get the absolute value of an int.
Added functions to support overflow for uints.
Added tests for the new functions.

the final file "overflow.gno" is very long (1000 lines). Is it good? or is it possible/necessary to cut in many files?

@jaekwon can you take a look as the old code is yours?

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.94%. Comparing base (8a62a28) to head (be92319).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2905      +/-   ##
==========================================
- Coverage   60.95%   60.94%   -0.01%     
==========================================
  Files         564      564              
  Lines       75273    75273              
==========================================
- Hits        45884    45878       -6     
- Misses      26019    26022       +3     
- Partials     3370     3373       +3     

Flag	Coverage Δ
contribs/gnodev	61.46% <ø> (ø)
contribs/gnofaucet	14.46% <ø> (ø)
gno.land	67.92% <ø> (ø)
gnovm	65.77% <ø> (ø)
misc/genstd	80.54% <ø> (ø)
misc/logos	19.88% <ø> (ø)
tm2	61.96% <ø> (-0.11%)	⬇️

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