mpp_split: tweak split parameters
mpp_split: tweak split parameters

Increases STARTING_CONFIGS to sample more starting configurations.
Reduces CANDIDATES_PER_LEVEL to reduce computational effort.
Increases REDISTRIBUTE.

The time it takes for a typical suggest_split call is about 2 msec a
desktop machine.

pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,wakiyamap/electrum-mona,wakiyamap/electrum-mona,pooler/electrum-ltc,spesmilo/electrum,wakiyamap/electrum-mona,wakiyamap/electrum-mona,spesmilo/electrum