Pull the mutable 'is_swizzled' semantic field from ast::MemberAccessorExpression and into a new semantic::MemberAccessorExpression node.
Have the TypeDeterminer create these semantic::MemberAccessorExpression nodes.
Bug: tint:390
Change-Id: I8fc6e36dabb417190528536a94d027af54059222
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/40142
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>