This CL adds a `location` value into the `Parameter` sem object.
This will be set if the parameter has an `@location` attribute
applied.
Bug: tint:1633
Change-Id: I55cb5cbda951f70d071ebe1400865b63af1fb20a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/101065
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>