sem: Split sem::Variable into global, local and parameter

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Change-Id: Ic8ac808088132b7bc2e43da6ce46a06571e0fed5
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/59200
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: James Price <jrprice@google.com>

src/ast/identifier_expression.h

@@ -16,7 +16,6 @@
 #define SRC_AST_IDENTIFIER_EXPRESSION_H_
 
 #include "src/ast/expression.h"
-#include "src/sem/intrinsic.h"
 
 namespace tint {
 namespace ast {