Support TMDs

[Radonirinaunimi]

This PR finally introduces the support for TMD distributions. The Subgrid layout has been extended to include the $k_T$ dependence and the shape now becomes $(A, \alpha_s, k_T, x, Q^2)$.

[github-actions]

🚀 Benchmark Results 🚀

Here are the results from the benchmark run.

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xfxq2                   time:   [1.1311 µs 1.1314 µs 1.1318 µs]
Found 5 outliers among 100 measurements (5.00%)
  1 (1.00%) high mild
  4 (4.00%) high severe

xfxq2s                  time:   [68.745 µs 69.012 µs 69.301 µs]
Found 22 outliers among 100 measurements (22.00%)
  17 (17.00%) low mild
  1 (1.00%) high mild
  4 (4.00%) high severe

xfxq2_members           time:   [621.16 ps 621.31 ps 621.51 ps]
Found 8 outliers among 100 measurements (8.00%)
  1 (1.00%) low mild
  5 (5.00%) high mild
  2 (2.00%) high severe

[github-actions]

🚀 Benchmark Results 🚀

Here are the results from the benchmark run.

xfxq2                   time:   [1.1287 µs 1.1300 µs 1.1320 µs]
                        change: [−0.4225% +0.0090% +0.6117%] (p = 0.99 > 0.05)
                        No change in performance detected.
Found 11 outliers among 100 measurements (11.00%)
  4 (4.00%) high mild
  7 (7.00%) high severe

xfxq2s                  time:   [68.104 µs 68.413 µs 68.791 µs]
                        change: [−1.5598% −0.7972% +0.0412%] (p = 0.05 > 0.05)
                        No change in performance detected.
Found 6 outliers among 100 measurements (6.00%)
  3 (3.00%) high mild
  3 (3.00%) high severe

xfxq2_members           time:   [621.28 ps 621.42 ps 621.60 ps]
                        change: [−0.0355% +0.0264% +0.0872%] (p = 0.42 > 0.05)
                        No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
  5 (5.00%) high mild
  5 (5.00%) high severe