Merge MR !43, 'jrwrigh/advection_div_diff_flux', into 'main'

Implement DivDiffFluxProjection for advection diffusion

See merge request phypid/honee!43

chore: Replace SetValueDefault with DMSet*

feat(advdif): Implement indirect div(F_diff) projection

feat(advdif): Add div F_diff into RHS

feat(qdata): Add BoundaryGradient for 2D

fix: Check if div_diff_flux requested, but not available

feat(dm): Add DMGetStratumISAtHeight

refactor(div F_diff): Change Setup arguments

style(div F_diff): Use `div_*` where appropriate

feat(div F_diff): Add GetOperatorFieldData

feat(div F_diff): Use function pointers for RHS Op creation

refactor(div F_diff): DMPlexCreateFaceLabel in Initialize

Also trade out usage of user->dm for projection->dm where appropriate

fix: QDataBoundaryGradientGet use central storage

style: restriction -> elem_restr for QDataBoundaryGrad

feat: Implement divergence of diffusive flux

fix: Copy label values when creating global array

The IS resulting from `DMLabelGetValueIS` is a pointer to the
`label->stratumValues` array, which has to maintain it's order. However,
we need a sor

fix: Copy label values when creating global array

The IS resulting from `DMLabelGetValueIS` is a pointer to the
`label->stratumValues` array, which has to maintain it's order. However,
we need a sorted array of the values for `PetscFindInt` to work
correctly. So we simply copy the array.

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fix(dm): CreateFaceLabel only if label doesn't exist

Also increase the label size to accommodate more than single-digit
dm_face values

style: Clean up velocity gradient projection

style: Clean up Grid Anisotropy code

feat: Remove CeedData qdata members

feat: Implement centralized storage of QData

Merge branch 'jrwrigh/misc_refactor' into 'main'

refactor: Clean up global struct members

See merge request phypid/honee!31

feat: Add jac_data_size_vol

- Allows non-Jacobian examples to not have to set zeros to it's inputs
- Removes the need for `uses_newtonian` (newtonian itself can not add
the extra term for IDL)

refactor: Replace dm_scale with meter

refactor: Remove q_data_size* from ProblemData