Add transform::Unshadow to renamed shadowed symbols. Required by a
number of other transforms.
Replace Resolver symbol resolution with dep-graph.
The dependency graph now performs full symbol resolution before the
regular resolver pass.
Make use of this instead of duplicating the effort.
Simplfies code, and actually performs variable shadowing consistently.
Fixed: tint:819
Bug: tint:1266
Change-Id: I595d1812aebe1d79d2d32e724ff90de36e74cf4b
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/70523
Reviewed-by: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Ben Clayton