[LegalizeTypes] Factor in vscale_range when widening insert_subvector

Currently when widening operands for insert_subvector nodes, we check
first that the indices are valid by seeing if the subvector is
statically known to be smaller than or equal to the in-place vector.

However if we're inserting a fixed subvector into a scalable vector we rely on
the minimum vector length of the latter. This patch extends the widening logic
to also take into account the minimum vscale from the vscale_range attribute,
so we can handle more scenarios where we know the scalable vector is large
enough to contain the subvector.

Fixes https://github.com/llvm/llvm-project/issues/63437

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D153519