xsave* also loads data

The xsave operation on x86 stores the processor state to the xsave area pointed to by the destination operand. But it also reads some data from the xsave header there. (https://www.felixcloutier.com/x86/xsave, https://www.felixcloutier.com/x86/xsaveopt). The decoder should mark it as also loading data.

Start by locating the x86 decoder handling the xsave and xsaveopt operations, then compare its current operand data-flow classification with the linked instruction documentation. Update the classification so the xsave area is marked as also loading data, and verify the behavior with the decoder's relevant tests if available.

Written by the indexing model from the issue text.