macos build and miri check to nightly

[harsha-simhadri]

Created nightly ci run; moved miri to nightly. added back macos build test.
Added status to readme.md

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.51%. Comparing base (9fe7053) to head (2a724bf).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1058   +/-   ##
=======================================
  Coverage   89.51%   89.51%           
=======================================
  Files         461      461           
  Lines       85920    85920           
=======================================
+ Hits        76911    76914    +3     
+ Misses       9009     9006    -3     

Flag	Coverage Δ
miri	89.51% <ø> (+<0.01%)	⬆️
unittests	89.14% <ø> (+<0.01%)	⬆️

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see 3 files with indirect coverage changes

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