[InstCombine] Infer inbounds for more GEPs of dereferenceable pointers

Use Value::getPointerDereferenceableBytes() instead of hardcoding dereferenceable only for allocas. Allows us to infer inbounds GEPs for other Values like CallInsts and Arguments.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D153815