Update CI setup

[penelopeysm]

This is broadly in line with what Turing / DynamicPPL has.

Main changes are:

• Bumping versions of actions
• Also changing 1.6 -> 'min' so that we don't have to update that in the future
• Also changing the 'nightly' test (brittle) to a new prerelease workflow
• Using aarch64 on macOS rather than x64

While doing this I found that the minimum Julia bound of 1.6 was not correct: AdvancedPS depends on Libtask 0.8, which sets a minimum bound of Julia 1.7, so I updated that too.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.59%. Comparing base (1e5dfdd) to head (7d2ef12).
Report is 13 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
+ Coverage   96.09%   96.59%   +0.49%     
==========================================
  Files           8        8              
  Lines         410      411       +1     
==========================================
+ Hits          394      397       +3     
+ Misses         16       14       -2     

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[coveralls]

Pull Request Test Coverage Report for Build 12927897864

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.5%) to 96.594%

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Totals
Change from base Build 12927587973:	0.5%
Covered Lines:	397
Relevant Lines:	411

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💛 - Coveralls

[mhauru]

Seems like solid improvements all around