Add Schwinger, Lee-Pomeransky and Baikov parametrization to FCFeymanParametrize.

[vsht]

FCFeynmanParametrize currently supports only Feynman parametrization. It would be good to have Schwinger, Lee-Pomeransky and Baikov working as well. At least for pure denominator integrals.

[vsht]

Lee-Pomeransky is already available (purely scalar case only), cf.

FCFeynmanParametrize[{SFAD[{ p1, m^2}], SFAD[{ p3, m^2}], 
   SFAD[{(p3 - p1), m^2}], SFAD[{{0, 2 p1 . n}}], SFAD[{{0, 2 p3 . n}}]}, {p1, p3}, 
  Names -> x, Method -> "Lee-Pomeransky", FCReplaceD -> {D -> 4 - 2 ep}, 
  FinalSubstitutions -> {SPD[n] -> 1, m -> 1}]

Baikov would require a bit more work though ...