Rework frexp as per #1329

[ckormanyos]

A billion no-hang runs locally. Lets progress here.

See also #1329

[ckormanyos]

OK the first draft of a non-hanging, yet clunky, version is in and cycling in CI.

Next steps involve:

• Add dedicated numerical checks at 32, 64, 128 bit. Testing on frexp is a bit light anyway and we could use some more.
• Optimize it, as there is ample room for improvement.

Cc: @mborland

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.8%. Comparing base (e72fd34) to head (7eb2727).

Files with missing lines	Patch %	Lines
include/boost/decimal/detail/cmath/frexp.hpp	87.5%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1330     +/-   ##
=========================================
- Coverage     98.8%   98.8%   -0.0%     
=========================================
  Files          278     278             
  Lines        18034   18052     +18     
  Branches      1918    1922      +4     
=========================================
+ Hits         17812   17826     +14     
- Misses         222     226      +4     

Files with missing lines	Coverage Δ
include/boost/decimal/detail/cmath/frexp.hpp	84.7% <87.5%> (-7.3%)	⬇️

... and 2 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e72fd34...7eb2727. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.