Refine combination of LHAPDF sets logics

[Radonirinaunimi]

Supports more varieties of PDF sets.

[github-actions]

🚀 Benchmark Results 🚀

Here are the results from the benchmark run.

xfxq2                   time:   [1.1206 µs 1.1268 µs 1.1383 µs]
Found 9 outliers among 100 measurements (9.00%)
  3 (3.00%) high mild
  6 (6.00%) high severe

xfxq2s                  time:   [67.364 µs 67.753 µs 68.275 µs]
Found 4 outliers among 100 measurements (4.00%)
  1 (1.00%) high mild
  3 (3.00%) high severe

xfxq2_members           time:   [621.40 ps 621.48 ps 621.57 ps]
Found 9 outliers among 100 measurements (9.00%)
  3 (3.00%) high mild
  6 (6.00%) high severe