feat: adds regex_extract function and more type tests (#7107)

* feat: adds format, regex_extract function and more type tests

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

* fix: forgot functions

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

* chore: forgot null type

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

* test: forgot date type

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

* feat: remove format function

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

* test: update results after upgrading datafusion

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

---------

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

tests/cases/standalone/common/function/string/length.sql

@@ -0,0 +1,58 @@
+-- String length function tests
+
+-- LENGTH function
+SELECT LENGTH('hello');
+
+SELECT LENGTH('');
+
+SELECT LENGTH(NULL);
+
+SELECT LENGTH('hello world');
+
+-- CHAR_LENGTH (character length)
+SELECT CHAR_LENGTH('hello');
+
+SELECT CHAR_LENGTH('');
+
+SELECT CHAR_LENGTH(NULL);
+
+-- CHARACTER_LENGTH (alias for CHAR_LENGTH)
+SELECT CHARACTER_LENGTH('hello world');
+
+-- Unicode character length
+SELECT LENGTH('世界') AS a, CHAR_LENGTH('世界') AS b;
+
+SELECT LENGTH('🚀🌟') AS a, CHAR_LENGTH('🚀🌟') AS b;
+
+SELECT LENGTH('café') AS a, CHAR_LENGTH('café') AS b;
+
+-- Test with table data
+CREATE TABLE length_test(s VARCHAR, ts TIMESTAMP TIME INDEX);
+
+INSERT INTO length_test VALUES
+    ('hello', 1000),
+    ('world!', 2000),
+    ('', 3000),
+    ('中文测试', 4000),
+    ('🚀🎉🌟', 5000),
+    (NULL, 6000);
+
+SELECT s, LENGTH(s) AS a, CHAR_LENGTH(s) AS b FROM length_test ORDER BY ts;
+
+-- BIT_LENGTH (length in bits)
+SELECT BIT_LENGTH('hello');
+
+SELECT BIT_LENGTH('');
+
+SELECT BIT_LENGTH('世界');
+
+-- OCTET_LENGTH (length in bytes)
+SELECT OCTET_LENGTH('hello');
+
+SELECT OCTET_LENGTH('');
+
+SELECT OCTET_LENGTH('世界');
+
+SELECT OCTET_LENGTH('🚀');
+
+DROP TABLE length_test;