Recommit "[LV] Inline CreateSplatIV call for scalar VFs."

This reverts the revert commit 073c27b5.

A reduced test case has been added in 5e4966cb and the code has
been updated to handle the case where getInductionOpcode returns
BinaryOpsEnd. In this case, the original code was always using
Instruction::Add. Do the same in the patch.

Note this commit may slightly change the value naming, because it now
also assigns the 'induction' name in the floating point case.