math.unsigned: fix rotate_left() for uint256, add test (#24872)

Author: tankf33der

vlib/math/unsigned/uint256.v

@@ -348,7 +348,7 @@ pub fn (u Uint256) rotate_left(k int) Uint256 {
 			return Uint256{u.hi, u.lo}
 		}
 
-		return Uint256{Uint128{u.hi.lo << n | u.lo.hi >> (64 - n), u.hi.hi << n | u.hi.lo >> (64 - n)}, Uint128{}}
+		return Uint256{Uint128{u.hi.lo << n | u.lo.hi >> (64 - n), u.hi.hi << n | u.hi.lo >> (64 - n)}, Uint128{u.lo.lo << n | u.hi.hi >> (64 - n), u.lo.hi << n | u.lo.lo >> (64 - n)}}
 	}
 	n -= 64
 	if n == 0 {

vlib/math/unsigned/uint256_test.v

@@ -303,3 +303,8 @@ fn test_lsh() {
 	assert a.lsh(200).str() == '197653379443855803891661337357963000110230968235283518742069248'
 	assert a.lsh(300) == unsigned.uint256_zero
 }
+
+fn test_rotate_left() {
+	a := unsigned.uint256_from_dec_str('25514942427378518882041616545065271187265095759155217686057363902268374351523')!
+	assert a.rotate_left(182).str() == '88706376393829417451765793453791860419270208590599379720310994108668904859637'
+}