Allowing direct CEL reserved keyword usage in CRD (#126188)

* automatically escape reserved keywords for direct usage

* Add reserved keyword support in a ratcheting way, add tests.

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Co-authored-by: Wenxue Zhao <ballista01@outlook.com>

test/integration/apiserver/cel/typeresolution_test.go

@@ -382,7 +382,7 @@ func simpleCompileCEL(schema *spec.Schema, expression string) (cel.Program, erro
 	}
 	declType := celopenapi.SchemaDeclType(schema, true).MaybeAssignTypeName("selfType")
 	rt := commoncel.NewDeclTypeProvider(declType)
-	opts, err := rt.EnvOptions(env.TypeProvider())
+	opts, err := rt.EnvOptions(env.CELTypeProvider())
 	if err != nil {
 		return nil, err
 	}