feat(stdlibs): add math and math/bits

[thehowl]

Great bug-finder package:

This adds packages math and math/bits, copied from go standard libraries with minimal modifications.

The changes from the standard libraries can be inspected with the following scripts:

cd path/to/stdlibs/math
for i in /usr/lib/go/src/math/*.go; do git diff --no-index "$i" "$(echo "$i" | sed 's#.*/\([^/]*\)\.go$#./\1.gno#g')"; done
cd bits
for i in /usr/lib/go/src/math/bits/*.go; do git diff --no-index "$i" "$(echo "$i" | sed 's#.*/\([^/]*\)\.go$#./\1.gno#g')"; done

These will generate a diff for each file in /usr/lib/src/go, and their gno counterpart in each directory.

Most changes involve removing the if haveXXXArch statements in the many functions which normally support being executed as native assembly instructions.

Additionally, within tests, all the dot imports present were removed (as they are not supported in Gno), and some bugs had to be worked around (I added references wherever this was the case).

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 ✅

Comparison is base (902e678) 55.94% compared to head (d038ed8) 48.26%.
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1153      +/-   ##
==========================================
- Coverage   55.94%   48.26%   -7.68%     
==========================================
  Files         420      377      -43     
  Lines       65477    64130    -1347     
==========================================
- Hits        36631    30955    -5676     
- Misses      25983    30731    +4748     
+ Partials     2863     2444     -419     

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[thehowl]

Draft until #1221

[thehowl]

I've now cleaned up the code in the PR, since we merged #1221 :) Reviews welcome!

[deelawn]

Can this block be removed as part of this PR?
https://github.com/gnolang/gno/blob/master/gnovm/tests/imports.go#L275-L282

[deelawn]

Looks good. As noted in my other comment, I think it would be slightly more correct to include the following files inside _test suffixed packages:

• all_test.gno
• bits_test.gno
• const_test.gno

I'm also happy to take care of these changes; just let me know.

[thehowl]

@deelawn just took care of the changes you requested.

export_test.go needs to be in package math specifically (it exposes internal functions). arguably, we don't need this (as we don't use internal cpu-specific instructions, so there's no 2 different implementations for the same function), but I'd say we keep it for now to maintain similarity with the Go stdlib as much as possible.

If this looks good I think we can probably merge later today. :)