ENH: fvMatrix, faMatrix: replace raw pointers with unique_ptr (#3107)

...solvers/multiphase/reactingMultiphaseEulerFoam/pUf/pEqn.H

src/finiteArea/faMatrices/faMatrix/faMatrix.C

src/finiteArea/faMatrices/faMatrix/faMatrix.H

...anSchemes/gaussFaLaplacianScheme/gaussFaLaplacianScheme.C

...lacianSchemes/gaussLaplacianScheme/gaussLaplacianScheme.C

...acianSchemes/gaussLaplacianScheme/gaussLaplacianSchemes.C

...aussLaplacianScheme/relaxedNonOrthoGaussLaplacianScheme.C

...ussLaplacianScheme/relaxedNonOrthoGaussLaplacianSchemes.C

src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.C

src/finiteVolume/fvMatrices/fvMatrix/fvMatrix.H