Fix alignment in acquire-release spec test (#9014)

Instructions like `i32.atomic.load8_u` have a different alignment than
the value of their argument. Add an extra `align` field to account for
this.

The value_type was also wrong for a few `load` operations, but this
didn't matter because loads don't use their `value_type`; it's only used
to choose what param to pass as the value for stores.