ENH: add wall-function blending treatments

    Please see the Extended Code Guide and header files for the details.

    ENH: add wall-function blending treatments to epsilonWallFunc
         adds `stepwise`, `max`, `binomial`, and `exponential` wall-function
         blending treatments:
    COMP: check backward compatibility for:
          `serial`
          `parallel`
          `serial restart`
          `parallel restart`
          computations in comparison to the following tutorials from v1906:
          `circuitBoardCooling  condensatingVessel  evaporationMultiComponent
           hotRoom  movingBox  multiRegionHeaterRadiation  reverseBurner
           solidQuenching2D`
    STYLE: simplify `forAll`s

    ENH: add new wall blending approaches into omegaWallFunction
         adds stepwise, max, binomial, and exponential wall function blending apprs.
         ensures/forces the backward compatibility:
           - blended = true    (blending:BINOMIAL2) (default)
           - blended = false   (blending:STEPWISE)
        simplifies forAlls
        deprecates objects:
           - "blended" - use "blending::" options
           - "includeG" - as was hardcoded

    ENH: add wall-func blending treatments into nutWallFuncs
    - nutWallFunction
    - nutUWallFunction
    - nutkWallFunction
    COMP: check backward compatibility for:
          - serial
          - parallel
          - serial restart
          - parallel restart
          computations in comparison to the following tutorials from v1906:
          - heatTransfer/buoyantSimpleFoam/buoyantCavity
          - compressible/rhoSimpleFoam/gasMixing/injectorPipe

    DOC: modify header docs in wallFuncs
    - nutUTabulatedWallFunction
    - nutUSpaldingWallFunction
    - nutURoughWallFunction
    - nutUBlendedWallFunction
      - REVERT: change write order
    - nutLowReWallFunction
    - kLowReWallFunction:
      - ENH: protect against zero-division error through 'Ceps2' entry
      - STYLE: remove few redundant empty lines