Remove namespace usage from 'fr'

[ChrisJefferson]

There is a plan that we might remove namespaces from GAP (code using '@'), because the implementation doesn't really work that well.

This PR is an experiment to see how Fr could be fixed, and how nice the code looks, without using '@'. I don't consider this PR a requirement to merge, and it might not even be the nicest way to do this! However, Fr is one of the biggest users of namespaces and '@'.

Similar to how I have handled similar issues in my own packages, I've added a global record 'Fr', and then put all the 'fr' methods inside that. The only place this doesn't work with with attributes / methods, so those I've prefixed with 'Fr_'.

One issue is we can't use 'BindGlobal' any more, so I just assign members of the record.

[codecov]

Codecov Report

❌ Patch coverage is 55.11412% with 531 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.67%. Comparing base (0cce6ee) to head (5d6138d).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
gap/linear.gi	18.54%	101 Missing ⚠️
gap/vector.gi	31.81%	90 Missing ⚠️
gap/group.gi	58.45%	86 Missing ⚠️
gap/helpers.gi	34.14%	81 Missing ⚠️
gap/examples.gi	47.12%	46 Missing ⚠️
gap/mealy.gi	72.12%	46 Missing ⚠️
gap/cp.gi	66.31%	32 Missing ⚠️
gap/algebra.gi	54.54%	15 Missing ⚠️
gap/frelement.gi	84.50%	11 Missing ⚠️
gap/perlist.gi	33.33%	8 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
- Coverage   55.68%   55.67%   -0.01%     
==========================================
  Files          25       25              
  Lines       15999    15996       -3     
==========================================
- Hits         8909     8906       -3     
  Misses       7090     7090              

Files with missing lines	Coverage Δ
gap/group.gd	100.00% <100.00%> (ø)
gap/helpers.gd	70.32% <100.00%> (ø)
gap/linear-gbnp.gi	17.85% <33.33%> (+3.04%)	⬆️
gap/bisets.gi	56.47% <66.66%> (ø)
gap/frmachine.gi	82.83% <94.56%> (+0.01%)	⬆️
gap/vhgroup.gi	66.77% <81.48%> (-0.11%)	⬇️
gap/perlist.gi	56.50% <33.33%> (ø)
gap/frelement.gi	88.10% <84.50%> (-0.02%)	⬇️
gap/algebra.gi	30.68% <54.54%> (ø)
gap/cp.gi	53.65% <66.31%> (ø)
... and 6 more

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[fingolfin]

Thank you, I like it! For some background, see also gap-system/gap#6079

But of course it is @laurentbartholdi who needs to decide.