PWGHF: Configure `TrackSelectorPID` objects in `init` in the selectors

[vkucera]

Avoid creating and configuring the TrackSelectorPID objects repeatedly in the candidate loop of selectors.
Instead, create the object as a struct member and configure it in the init function.

• candidateSelectorB0ToDPi @AlexBigO PWGHF: Add QA histograms in Dplus and B0 selectors, follow issue #2257 and add histograms for prongs in acceptance in B0 task #2299
• candidateSelectorDplusToPiKPi @AlexBigO PWGHF: Add QA histograms in Dplus and B0 selectors, follow issue #2257 and add histograms for prongs in acceptance in B0 task #2299

[vkucera]

Fixed in #3244