Add conversion CalciumField, QQBar -> Float64

[fingolfin]

Work towards #1650

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.51%. Comparing base (0271fc0) to head (6100f3e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1893      +/-   ##
==========================================
- Coverage   87.51%   87.51%   -0.01%     
==========================================
  Files          97       97              
  Lines       35532    35536       +4     
==========================================
+ Hits        31096    31098       +2     
- Misses       4436     4438       +2     

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[fingolfin]

Updated, added also conversion from CalciumField to Float64, so this PR should now be ready 🥳

[lgoettgens]

@benlorenz another instance where vinberg_2.jlcon needs absurd time: https://github.com/Nemocas/Nemo.jl/actions/runs/11607921085/job/32322223087?pr=1893#step:7:20023 cancelled by hand after about an hour in this single file