Revert rG1b7089fe "[SLP] Add...

Revert rG1b7089fe "[SLP] Add ScalarizationOverheadBuilder helper to track vector extractions"
Revert rGef89409a "Fix 'unused-lambda-capture' gcc warning. NFCI."
Revert rG926ccfef "[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.