Fix USING TIMEOUT time generation (#299)

Scylla does not support fractions.
We need to make sure that time is formatted the following way: XmYsZms

qb/utils_test.go

@@ -0,0 +1,61 @@
+package qb
+
+import (
+	"testing"
+	"time"
+)
+
+func TestFormatDuration(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    time.Duration
+		expected string
+	}{
+		{
+			name:     "Zero duration",
+			input:    0,
+			expected: "",
+		},
+		{
+			input:    500 * time.Millisecond,
+			expected: "500ms",
+		},
+		{
+			input:    10 * time.Second,
+			expected: "10s",
+		},
+		{
+			input:    3 * time.Minute,
+			expected: "3m",
+		},
+		{
+			input:    (2 * time.Minute) + (30 * time.Second),
+			expected: "2m30s",
+		},
+		{
+			input:    (15 * time.Second) + (250 * time.Millisecond),
+			expected: "15s250ms",
+		},
+		{
+			input:    (1 * time.Minute) + (45 * time.Second) + (123 * time.Millisecond),
+			expected: "1m45s123ms",
+		},
+		{
+			input:    (5 * time.Minute) + (1 * time.Second) + (999 * time.Millisecond),
+			expected: "5m1s999ms",
+		},
+		{
+			input:    (2 * time.Second) + (1500 * time.Millisecond), // 3 seconds, 500ms
+			expected: "3s500ms",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			actual := formatDuration(tt.input)
+			if actual != tt.expected {
+				t.Errorf("got %q, want %q", actual, tt.expected)
+			}
+		})
+	}
+}