Changing face to facet in variable names, struct fields, and docstrings

[KnutAM]

Except direct field access of (fqr::FacetQuadratureRule).face_rules, this PR should not have any influence downstream AFAICS.

[codecov]

Codecov Report

Attention: Patch coverage is 99.25373% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.57%. Comparing base (b8f986a) to head (c27cad6).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Quadrature/quadrature.jl	88.88%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1123   +/-   ##
=======================================
  Coverage   93.57%   93.57%           
=======================================
  Files          39       39           
  Lines        6073     6073           
=======================================
  Hits         5683     5683           
  Misses        390      390           

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[termi-official]

Still some left

Grid/grid.jl:350:### Mesh interface ###
Grid/grid.jl:385:        facesets = nothing, # deprecated
Grid/grid.jl:389:    if facesets !== nothing
Grid/grid.jl:392:            for (key, set) in facesets
Grid/grid.jl:531:Returns all faces as `FacetIndex` in the set with name `setname`.
Grid/grid.jl:639:boundaryfunction(::Type{FaceIndex}) = faces
Grid/grid.jl:651:        #To be able to do a,b = faceidx
Grid/grid.jl:654:        # Necessary to check if, e.g. `(cellid, faceidx) in faceset`
Grid/grid.jl:688:    SurfaceOrientationInfo
Grid/grid.jl:693:Take for example the faces
Grid/grid.jl:699:which are rotated against each other by 90° (shift index is 1) or the faces

FEValues/FacetValues.jl:123:@inline function reinit!(fv::FacetValues, x::AbstractVector, face_nr::Int)
FEValues/FacetValues.jl:124:    return reinit!(fv, nothing, x, face_nr)
FEValues/FacetValues.jl:127:function reinit!(fv::FacetValues, cell::Union{AbstractCell, Nothing}, x::AbstractVector{Vec{dim, T}}, face_nr::Int) where {dim, T}
FEValues/FacetValues.jl:142:    @inbounds for (q_point, w) in pairs(getweights(fv.fqr, face_nr))
FEValues/FacetValues.jl:146:        weight_norm = weighted_normal(J, getrefshape(geo_mapping.ip), face_nr)

Queriev with ack -v "facet" | ack "face" and some manual filtering.

[KnutAM]

Thanks!
Fixed,

• Grid/grid.jl:531:Returns all faces as `FacetIndex` in the set with name `setname`.
• Grid/grid.jl:651: #To be able to do a,b = faceidx
• Grid/grid.jl:654: # Necessary to check if, e.g. `(cellid, faceidx) in faceset`
• All (and some more) in FacetValues.jl

In the grid constructor, it is correct to have face, also in the SurfaceOrientationInfo (Should formally now be FaceOrientationInfo and EdgeOrientationInfo IMO, and this should be changed before implemented and made public (if that's the plan).

There is also a default FaceIndex in BCValues that I saw now, but I'll do this in a separate PR since this PR aims to only do internal renaming (except the mentioned exception).