Add `FuzzUtilMergeSets`

[MarvinJWendt]

Add FuzzUtilMergeSets after #149 is done.

// FuzzUtilMergeSets merges multiple test sets into one.
// All test sets must have the same type.
//
// Example:
//  mergedSet := testza.FuzzUtilMergeSets(testza.FuzzIntGenerateRandomNegative(3, 0), testza.FuzzIntGenerateRandomPositive(2, 0))
func FuzzUtilMergeSets[setType any](sets ...[]setType) (merged []setType) {
    for _, set := range sets {
        merged = append(merged, set...)
    }

    return merged
}

[MarvinJWendt]

Should also use #156