chore: simplify map const (#18440)

## Which issue does this PR close?


## Rationale for this change

map const wont be simplified, the comment says "TODO: support the
optimization for `Map` type after support impl hash for it", but it
seems that hash is already supported for map.

## What changes are included in this PR?

remove the todo

## Are these changes tested?

UT

## Are there any user-facing changes?

No

Author: chenkovsky

datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs

@@ -722,35 +722,12 @@ impl<'a> ConstEvaluator<'a> {
                 } else {
                     // Non-ListArray
                     match ScalarValue::try_from_array(&a, 0) {
-                        Ok(s) => {
-                            // TODO: support the optimization for `Map` type after support impl hash for it
-                            if matches!(&s, ScalarValue::Map(_)) {
-                                ConstSimplifyResult::SimplifyRuntimeError(
-                                    DataFusionError::NotImplemented("Const evaluate for Map type is still not supported".to_string()),
-                                    expr,
-                                )
-                            } else {
-                                ConstSimplifyResult::Simplified(s, metadata)
-                            }
-                        }
+                        Ok(s) => ConstSimplifyResult::Simplified(s, metadata),
                         Err(err) => ConstSimplifyResult::SimplifyRuntimeError(err, expr),
                     }
                 }
             }
-            ColumnarValue::Scalar(s) => {
-                // TODO: support the optimization for `Map` type after support impl hash for it
-                if matches!(&s, ScalarValue::Map(_)) {
-                    ConstSimplifyResult::SimplifyRuntimeError(
-                        DataFusionError::NotImplemented(
-                            "Const evaluate for Map type is still not supported"
-                                .to_string(),
-                        ),
-                        expr,
-                    )
-                } else {
-                    ConstSimplifyResult::Simplified(s, metadata)
-                }
-            }
+            ColumnarValue::Scalar(s) => ConstSimplifyResult::Simplified(s, metadata),
         }
     }
 }

datafusion/sqllogictest/test_files/simplify_expr.slt

@@ -107,3 +107,14 @@ query B
 SELECT a / NULL::DECIMAL(4,3) > 1.2::decimal(2,1) FROM VALUES (1) AS t(a);
 ----
 NULL
+
+query TT
+explain SELECT CASE WHEN 1 > 0 THEN MAP {'x': 100} ELSE MAP {'y': 200} END AS a;
+----
+logical_plan
+01)Projection: Map([{"x":"100"}]) AS a
+02)--EmptyRelation: rows=1
+physical_plan
+01)ProjectionExec: expr=[[{x:100}] as a]
+02)--PlaceholderRowExec
+