Replace more uses of isFOO by is_foo

[fingolfin]

No description provided.

[fingolfin]

There is a failure in Run long tests / test (1.9, x64, macOS-latest) (pull_request) but I can't tell what it is / if it is related to this PR or not.

@thofma perhaps you could restart it? It would be nice to get this merged so I can proceed with the alias deprecations.

[fingolfin]

@thofma it seems you already restarted it twice before and it keeps running into an infinite loop. So perhaps there is a genuine issue here? But what could that be? weird

[thofma]

Nah, it is "normal".

[codecov]

Codecov Report

Merging #1270 (809b699) into master (0fd09c1) will increase coverage by 67.82%.
Report is 4 commits behind head on master.
The diff coverage is 85.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #1270       +/-   ##
===========================================
+ Coverage    6.62%   74.45%   +67.82%     
===========================================
  Files         346      346               
  Lines      111179   111321      +142     
===========================================
+ Hits         7370    82879    +75509     
+ Misses     103809    28442    -75367     

Files	Coverage Δ
src/AlgAss/AbsAlgAss.jl	91.71% <100.00%> (+91.71%)	⬆️
src/AlgAss/Ramification.jl	100.00% <100.00%> (+100.00%)	⬆️
src/EllCrv/EllCrv.jl	95.57% <100.00%> (+95.57%)	⬆️
src/EllCrv/Heights.jl	92.43% <100.00%> (+92.43%)	⬆️
src/EllCrv/LocalData.jl	89.59% <100.00%> (+89.59%)	⬆️
src/EllCrv/ModularPolynomials.jl	100.00% <100.00%> (+100.00%)	⬆️
src/EllCrv/Torsion.jl	90.46% <100.00%> (+90.46%)	⬆️
src/GrpAb/GrpAbFinGen.jl	80.29% <100.00%> (+78.52%)	⬆️
src/HypellCrv/HypellCrv.jl	82.70% <100.00%> (+82.70%)	⬆️
src/Misc/Poly.jl	62.11% <100.00%> (+50.91%)	⬆️
... and 9 more

... and 286 files with indirect coverage changes