STYLE: wall functions: use more modern coding practices

The most frequent changes have been as follows.

from:

    tmp<scalarField> tuTau(new scalarField(patch().size(), Zero));
    scalarField& uTau = tuTau.ref();

to:

    auto tuTau = tmp<scalarField>::New(patch().size(), Zero);
    auto& uTau = tuTau.ref();

- Other changes involved the addition of - wherever approapriate -:

    const
    noexcept
    auto