Change SubexpressionOptimizer to leverage mutable exprs

PiperOrigin-RevId: 627065192

Author: l46kok

common/src/main/java/dev/cel/common/CelSource.java

@@ -279,6 +279,12 @@ public Builder clearMacroCall(long exprId) {
       return this;
     }
 
+    @CanIgnoreReturnValue
+    public Builder clearMacroCalls() {
+      this.macroCalls.clear();
+      return this;
+    }
+
     public ImmutableSet<Extension> getExtensions() {
       return extensions.build();
     }

optimizer/src/main/java/dev/cel/optimizer/AstMutator.java

@@ -242,9 +242,8 @@ public CelMutableAst renumberIdsConsecutively(CelMutableAst mutableAst) {
    * @param newResultPrefix Prefix to use for new comprehensin result identifier names.
    */
   public MangledComprehensionAst mangleComprehensionIdentifierNames(
-      CelAbstractSyntaxTree ast, String newIterVarPrefix, String newResultPrefix) {
-    CelNavigableMutableAst navigableMutableAst =
-        CelNavigableMutableAst.fromAst(CelMutableAst.fromCelAst(ast));
+      CelMutableAst ast, String newIterVarPrefix, String newResultPrefix) {
+    CelNavigableMutableAst navigableMutableAst = CelNavigableMutableAst.fromAst(ast);
     Predicate<CelNavigableMutableExpr> comprehensionIdentifierPredicate = x -> true;
     comprehensionIdentifierPredicate =
         comprehensionIdentifierPredicate

optimizer/src/main/java/dev/cel/optimizer/optimizers/BUILD.bazel

@@ -46,8 +46,10 @@ java_library(
         "//common",
         "//common:compiler_common",
         "//common/ast",
+        "//common/ast:mutable_ast",
         "//common/navigation",
         "//common/navigation:common",
+        "//common/navigation:mutable_navigation",
         "//common/types",
         "//common/types:type_providers",
         "//extensions:optional_library",