[LV] Disable fold tail by masking when IV is used outside (#81609)

When induction variable are used outside the loop body, tail folding
by masking mis-compiles, because for users outside of the loop the
final value of the induction is computed separately from the vector
loop.

Fixes https://github.com/llvm/llvm-project/issues/76069
Fixes https://github.com/llvm/llvm-project/issues/51677