STYLE: use zeroGradientType() instead of hard-coded or typeName

...hericModels/functionObjects/ObukhovLength/ObukhovLength.C

...nModels/diffusionMulticomponent/diffusionMulticomponent.C

...DissipationDiffusionModel/eddyDissipationDiffusionModel.C

...cFaMesh/interfaceTrackingFvMesh/interfaceTrackingFvMesh.C

src/finiteArea/finiteArea/fac/facEdgeIntegrate.C

...eArea/gradSchemes/leastSquaresFaGrad/leastSquaresFaGrad.C

src/finiteVolume/cfdTools/general/CorrectPhi/CorrectPhi.C

src/finiteVolume/finiteVolume/fvc/fvcSmooth/fvcSmooth.C

...teVolume/fvMesh/fvMeshSubset/fvMeshSubsetProxyTemplates.C

...tchDistMethods/patchDistMethod/patchDistMethodTemplates.C

src/functionObjects/field/CourantNo/CourantNo.C

src/functionObjects/field/age/age.C

src/functionObjects/field/blendingFactor/blendingFactor.C

...onIndexModels/resolutionIndexModel/resolutionIndexModel.C

...s/field/stabilityBlendingFactor/stabilityBlendingFactor.C

...unctionObjects/field/zeroGradient/zeroGradientTemplates.C

src/functionObjects/utilities/solverInfo/solverInfo.C

...otionDiffusivity/inverseVolume/inverseVolumeDiffusivity.C

...fusivity/motionDirectional/motionDirectionalDiffusivity.C

...ion/patchCorrected/patchCorrectedInterpolationTemplates.C