[mlir] Change vector.transfer_read/write "masked" attribute to "in_bounds".

This is in preparation for adding a new "mask" operand. The existing "masked" attribute was used to specify dimensions that may be out-of-bounds. Such transfers can be lowered to masked load/stores. The new "in_bounds" attribute is used to specify dimensions that are guaranteed to be within bounds. (Semantics is inverted.)

Differential Revision: https://reviews.llvm.org/D99639