Revert rG1b7089fe67b924bdd5ecef786a34bdba7a88778f "[SLP] Add...

Revert rG1b7089fe67b924bdd5ecef786a34bdba7a88778f "[SLP] Add ScalarizationOverheadBuilder helper to track vector extractions"
Revert rGef89409a59f3b79ae143b33b7d8e6ee6285aa42f "Fix 'unused-lambda-capture' gcc warning. NFCI."
Revert rG926ccfef032d206dcbcdf74ca1e3a9ebf4d1be45 "[SLP] ScalarizationOverheadBuilder - demand all elements for scalarization if the extraction index is unknown / out of bounds"

Revert ScalarizationOverheadBuilder sequence from D134605 - when accumulating extraction costs by Type (instead of specific Value), we are not distinguishing enough when they are coming from the same source or not, and we always just count the cost once. This needs addressing before we can use getScalarizationOverhead properly.