Add test for changing column's type by performing ADD COLUMN + UPDATE + DROP COLUMN.

tests/queries/0_stateless/01456_modify_column_type_via_add_drop_update.reference

+a	b	c	d	e
+Int64	String	UInt8	Float64	UInt32
+0	0	0	0	0
+1	2	3	4	5
+2	4	6	8	10
+3	6	9	12	15
+4	8	12	16	20
+5	10	15	20	25
+6	12	18	24	30
+7	14	21	28	35
+8	16	24	32	40
+9	18	27	36	45
+a	b	c	d	e
+Int64	String	UInt8	Float64	UInt32
+0	0	0	0	0
+1	2	3	4	5
+2	4	6	8	10
+3	6	9	12	15
+4	8	12	16	20
+5	10	15	20	25
+6	12	18	24	30
+7	14	21	28	35
+8	16	24	32	40
+9	18	27	36	45

tests/queries/0_stateless/01456_modify_column_type_via_add_drop_update.sql

+DROP TABLE IF EXISTS tbl;
+CREATE TABLE tbl(a String, b UInt32, c Float64, d Int64, e UInt8) ENGINE=MergeTree ORDER BY tuple();
+INSERT INTO tbl SELECT number, number * 2, number * 3, number * 4, number * 5 FROM system.numbers LIMIT 10;
+
+-- Change the types of columns by adding a temporary column and updating and dropping.
+-- Alters should be executed in sequential order.
+ALTER TABLE tbl ADD COLUMN xi Int64;
+ALTER TABLE tbl UPDATE xi = a WHERE 1;
+ALTER TABLE tbl DROP COLUMN a;
+ALTER TABLE tbl ADD COLUMN a Int64;
+ALTER TABLE tbl UPDATE a = xi WHERE 1;
+ALTER TABLE tbl DROP COLUMN xi;
+
+ALTER TABLE tbl ADD COLUMN xi String;
+ALTER TABLE tbl UPDATE xi = b WHERE 1;
+ALTER TABLE tbl DROP COLUMN b;
+ALTER TABLE tbl ADD COLUMN b String;
+ALTER TABLE tbl UPDATE b = xi WHERE 1;
+ALTER TABLE tbl DROP COLUMN xi;
+
+ALTER TABLE tbl ADD COLUMN xi UInt8;
+ALTER TABLE tbl UPDATE xi = c WHERE 1;
+ALTER TABLE tbl DROP COLUMN c;
+ALTER TABLE tbl ADD COLUMN c UInt8;
+ALTER TABLE tbl UPDATE c = xi WHERE 1;
+ALTER TABLE tbl DROP COLUMN xi;
+
+ALTER TABLE tbl ADD COLUMN xi Float64;
+ALTER TABLE tbl UPDATE xi = d WHERE 1;
+ALTER TABLE tbl DROP COLUMN d;
+ALTER TABLE tbl ADD COLUMN d Float64;
+ALTER TABLE tbl UPDATE d = xi WHERE 1;
+ALTER TABLE tbl DROP COLUMN xi;
+
+ALTER TABLE tbl ADD COLUMN xi UInt32;
+ALTER TABLE tbl UPDATE xi = e WHERE 1;
+ALTER TABLE tbl DROP COLUMN e;
+ALTER TABLE tbl ADD COLUMN e UInt32;
+ALTER TABLE tbl UPDATE e = xi WHERE 1;
+ALTER TABLE tbl DROP COLUMN xi;
+
+SELECT * FROM tbl FORMAT TabSeparatedWithNamesAndTypes;
+
+DROP TABLE tbl;
+
+-- Do the same thing again but with MODIFY COLUMN.
+CREATE TABLE tbl(a String, b UInt32, c Float64, d Int64, e UInt8) ENGINE=MergeTree ORDER BY tuple();
+INSERT INTO tbl SELECT number, number * 2, number * 3, number * 4, number * 5 FROM system.numbers LIMIT 10;
+ALTER TABLE tbl MODIFY COLUMN a Int64, MODIFY COLUMN b String, MODIFY COLUMN c UInt8, MODIFY COLUMN d Float64, MODIFY COLUMN e UInt32;
+SELECT * FROM tbl FORMAT TabSeparatedWithNamesAndTypes;
+
+DROP TABLE tbl;