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/upper_lower.sql

@@ -0,0 +1,93 @@
+-- String case conversion function tests
+
+-- Basic UPPER and LOWER functions
+SELECT UPPER('hello world');
+
+SELECT LOWER('HELLO WORLD');
+
+SELECT UPPER('MiXeD cAsE');
+
+SELECT LOWER('MiXeD cAsE');
+
+-- INITCAP (capitalize first letter of each word)
+SELECT INITCAP('hello world');
+
+SELECT INITCAP('HELLO WORLD');
+
+SELECT INITCAP('mIxEd CaSe TeSt');
+
+-- Test with NULL
+SELECT UPPER(NULL);
+
+SELECT LOWER(NULL);
+
+SELECT INITCAP(NULL);
+
+-- Test with numbers and special characters
+SELECT UPPER('hello123!@#');
+
+SELECT LOWER('HELLO123!@#');
+
+SELECT INITCAP('hello-world_test');
+
+-- Test with table data
+CREATE TABLE case_test("name" VARCHAR, city VARCHAR, ts TIMESTAMP TIME INDEX);
+
+INSERT INTO case_test VALUES
+    ('john doe', 'new york', 1000),
+    ('JANE SMITH', 'LOS ANGELES', 2000),
+    ('Bob Wilson', 'Chicago', 3000),
+    ('alice johnson', 'BOSTON', 4000);
+
+-- Apply case functions to table data
+SELECT "name", UPPER("name"), LOWER("name"), INITCAP("name") FROM case_test ORDER BY ts;
+
+SELECT city, UPPER(city), LOWER(city), INITCAP(city) FROM case_test ORDER BY ts;
+
+-- Combined case operations
+SELECT INITCAP(LOWER("name")) as formatted_name FROM case_test ORDER BY ts;
+
+-- Unicode case conversion
+SELECT UPPER('café');
+
+SELECT LOWER('CAFÉ');
+
+-- German characters
+SELECT UPPER('äöüß');
+
+-- German uppercase
+SELECT LOWER('ÄÖÜ');
+
+-- Greek letters
+SELECT UPPER('αβγ');
+
+SELECT LOWER('ΑΒΓ');
+
+-- Test with empty string
+SELECT UPPER('');
+
+SELECT LOWER('');
+
+SELECT INITCAP('');
+
+-- Test with single characters
+SELECT UPPER('a'), UPPER('A'), UPPER('1'), UPPER(' ');
+
+SELECT LOWER('a'), LOWER('A'), LOWER('1'), LOWER(' ');
+
+SELECT INITCAP('a'), INITCAP('A'), INITCAP('1');
+
+-- Complex Unicode examples
+CREATE TABLE unicode_case(s VARCHAR, ts TIMESTAMP TIME INDEX);
+
+INSERT INTO unicode_case VALUES
+    ('hello 世界', 1000),
+    ('HELLO 世界', 2000),
+    ('café à paris', 3000),
+    ('CAFÉ À PARIS', 4000);
+
+SELECT s, UPPER(s), LOWER(s), INITCAP(s) FROM unicode_case ORDER BY ts;
+
+DROP TABLE case_test;
+
+DROP TABLE unicode_case;