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/position.sql

@@ -0,0 +1,84 @@
+-- String position/search function tests
+
+-- POSITION function
+SELECT POSITION('world' IN 'hello world');
+
+SELECT POSITION('xyz' IN 'hello world');
+
+SELECT POSITION('' IN 'hello world');
+
+SELECT POSITION('world' IN '');
+
+-- STRPOS function (same as POSITION)
+SELECT STRPOS('hello world', 'world');
+
+SELECT STRPOS('hello world', 'xyz');
+
+SELECT STRPOS('hello world', 'hello');
+
+SELECT STRPOS('hello world', 'o');
+
+-- INSTR function
+SELECT INSTR('hello world', 'world');
+
+SELECT INSTR('hello world', 'o');
+
+SELECT INSTR('hello world', 'xyz');
+
+-- Case sensitive search
+SELECT POSITION('WORLD' IN 'hello world');
+
+SELECT POSITION('World' IN 'hello world');
+
+-- LEFT and RIGHT functions
+SELECT LEFT('hello world', 5);
+
+SELECT RIGHT('hello world', 5);
+
+-- More than string length
+SELECT LEFT('hello', 10);
+
+-- More than string length
+SELECT RIGHT('hello', 10);
+
+-- Test with NULL values
+SELECT POSITION('world' IN NULL);
+
+SELECT POSITION(NULL IN 'hello world');
+
+SELECT LEFT(NULL, 5);
+
+SELECT RIGHT('hello', NULL);
+
+-- Test with table data
+CREATE TABLE position_test(s VARCHAR, "search" VARCHAR, ts TIMESTAMP TIME INDEX);
+
+INSERT INTO position_test VALUES
+    ('hello world', 'world', 1000),
+    ('hello world', 'hello', 2000),
+    ('hello world', 'xyz', 3000),
+    ('programming', 'gram', 4000),
+    ('database', 'base', 5000);
+
+SELECT s, "search", POSITION("search" IN s) AS a, STRPOS(s, "search") AS b FROM position_test ORDER BY ts;
+
+-- Test LEFT and RIGHT with table data
+SELECT s, LEFT(s, 5), RIGHT(s, 5) FROM position_test ORDER BY ts;
+
+-- Unicode position tests
+SELECT POSITION('世' IN 'hello世界');
+
+SELECT POSITION('界' IN 'hello世界');
+
+SELECT STRPOS('café shop', 'é');
+
+SELECT LEFT('中文测试', 2);
+
+SELECT RIGHT('中文测试', 2);
+
+-- Multiple occurrences (finds first one)
+SELECT POSITION('o' IN 'hello world');
+
+SELECT STRPOS('hello world', 'l');
+
+DROP TABLE position_test;