WIP: Refactors QR and Cholesky factorization codes

The primary goal of this refactor is to subsume the pivoted QR and Cholesky factorizations into the functions that previously only computed the ordinary (non-pivoted) factorizations

- Deprecates `qrp`, `qrpfact`, `qrpfact`, `cholpfact`, `cholpfact!`
- Adds positional `pivoted::Bool` argument to `qr`, `qrfact`, `qrpfact!`, `cholfact`, and `cholfact!`
- Reorganizes QR factorizations section so that methods common to `QR`, `QRPackedQ`, `QRPivoted`, `QRPivotedQ` are grouped together.