Support Julia 1.12

[eschnett]

Closes #64

[codecov]

Codecov Report

❌ Patch coverage is 43.90244% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.15%. Comparing base (7c34681) to head (26886b2).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/MappedArrays.jl	43.90%	23 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (7c34681) and HEAD (26886b2). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (7c34681)	HEAD (26886b2)
	9	6

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #65       +/-   ##
===========================================
- Coverage   85.60%   73.15%   -12.46%     
===========================================
  Files           1        1               
  Lines         132      149       +17     
===========================================
- Hits          113      109        -4     
- Misses         19       40       +21     

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[eschnett]

I do not think there is a good way to get nice output for closures with Julia 1.12. The closures themselves are more complex, they contains type checks etc., and reconstituting x -> x*x would now be a major effort. If we wanted this then we should probably use an external package for this, or maybe modify Julia itself to keep a pretty-printable syntax tree around.

@timholy CI should now be working – can you approve running the CI workflow?