Switch from FiniteField to finite_field

[fingolfin]

Command used to create this PR:

git grep -l -w FiniteField | xargs perl -pi -e 's;\bFiniteField\b;finite_field;g'

[codecov]

Codecov Report

Merging #2872 (83f5747) into master (5d5ac29) will decrease coverage by 0.05%.
Report is 1 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2872      +/-   ##
==========================================
- Coverage   80.53%   80.48%   -0.05%     
==========================================
  Files         456      456              
  Lines       65208    65208              
==========================================
- Hits        52512    52485      -27     
- Misses      12696    12723      +27     

Files	Coverage Δ
...l/StandardFiniteFields/src/StandardFiniteFields.jl	88.92% <100.00%> (ø)
src/GAP/iso_gap_oscar.jl	91.89% <ø> (ø)
src/GAP/iso_oscar_gap.jl	98.55% <ø> (ø)
src/Rings/MPolyMap/MPolyRing.jl	88.63% <ø> (ø)
src/Serialization/Fields.jl	94.06% <100.00%> (ø)
src/TropicalGeometry/valuation.jl	71.34% <100.00%> (ø)

... and 5 files with indirect coverage changes

[fingolfin]

Hrmpf, failures are once again of this kind (and thus not caused by this PR):

Arithmetic for Finite field of degree 1 over GF(3): Error During Test at /home/runner/work/Oscar.jl/Oscar.jl/test/Rings/AlgClosureFp.jl:89
  Test threw exception
  Expression: a * (b + c) == a * b + a * c
  MethodError: objects of type Nothing are not callable
  Stacktrace:
   [1] (::fqPolyRepField)(b::fqPolyRepFieldElem)
     @ Nemo ~/.julia/packages/Nemo/iAwYA/src/flint/fq_nmod.jl:660
   [2] op(f::typeof(+), a::AlgClosureElem{fqPolyRepField}, b::AlgClosureElem{fqPolyRepField})
     @ Oscar.AlgClosureFp ~/work/Oscar.jl/Oscar.jl/src/Rings/AlgClosureFp.jl:129
   [3] +(a::AlgClosureElem{fqPolyRepField}, b::AlgClosureElem{fqPolyRepField})
     @ Oscar.AlgClosureFp ~/work/Oscar.jl/Oscar.jl/src/Rings/AlgClosureFp.jl:132

@fieker would be really good if we could do something about this :-(