[Enhance] Add prepare phase for some timestamp functions (#3947)

Fix: #3946 

CL:
1. Add prepare phase for `from_unixtime()`, `date_format()` and `convert_tz()` functions, to handle the format string once for all.
2. Find the cctz timezone when init `runtime state`, so that don't need to find timezone for each rows.
3. Add constant rewrite rule for `utc_timestamp()`
4. Add doc for `to_date()`
5. Comment out the `push_handler_test`, it can not run in DEBUG mode, will be fixed later.
6. Remove `timezone_db.h/cpp` and add `timezone_utils.h/cpp`

The performance shows bellow:

11,000,000 rows

SQL1: `select count(from_unixtime(k1)) from tbl1;`
Before: 8.85s
After: 2.85s

SQL2: `select count(from_unixtime(k1, '%Y-%m-%d %H:%i:%s')) from tbl1 limit 1;`
Before: 10.73s
After: 4.85s

The date string format seems still slow, we may need a further enhancement about it.

docs/en/sql-reference/sql-functions/date-time-functions/to_date.md

@@ -0,0 +1,48 @@
+---
+{
+    "title": "to_date",
+    "language": "en"
+}
+---
+
+<!-- 
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# to_date
+## description
+### Syntax
+
+`DATE TO_DATE(DATETIME)`
+
+Return the DATE part of DATETIME value.
+
+## example
+
+```
+mysql> select to_date("2020-02-02 00:00:00");
++--------------------------------+
+| to_date('2020-02-02 00:00:00') |
++--------------------------------+
+| 2020-02-02                     |
++--------------------------------+
+```
+
+##keyword
+
+    TO_DATE