tests: refactor: take use of secp256k1_ge_x_on_curve_var #1357

1. 
   theStack commented at 8:23 pm on June 25, 2023: contributor

   The recently merged ellswift PR (#1129) introduced a helper secp256k1_ge_x_on_curve_var to check if a given X coordinate is on the curve (i.e. the expression x^3 + 7 is square, see commit 79e5b2a8b80f507e2c9936ff1c4e2fb39bc66a4e). This can be used for code deduplication in the ecmult_const_mult_xonly test.

   (Found this instance via $ git grep add_int.*SECP256K1_B, I think it’s the only one where the helper can be used.)

2. tests: refactor: take use of `secp256k1_ge_x_on_curve_var`

   The recently merged ellswift PR (#1129) introduced a helper
   `secp256k1_ge_x_on_curve_var` to check if a given X coordinate is
   valid (i.e. the expression x^3 + 7 is square, see commit
   79e5b2a8b80f507e2c9936ff1c4e2fb39bc66a4e). This can be used for code
   deduplication in the `ecmult_const_mult_xonly` test.

   7d8d5c86df
3. theStack force-pushed on Jun 25, 2023
4. real-or-random approved
5. 
   real-or-random commented at 8:39 am on June 26, 2023: contributor

   utACK 7d8d5c86df8b27b45e80ed50341dd0ce64546c0f
6. real-or-random added the label refactor on Jun 26, 2023
7. 
   sipa commented at 6:09 pm on June 26, 2023: contributor

   utACK 7d8d5c86df8b27b45e80ed50341dd0ce64546c0f
8. real-or-random merged this on Jun 27, 2023
9. real-or-random closed this on Jun 27, 2023

   ---

10. theStack deleted the branch on Jun 27, 2023
11. vmta referenced this in commit 8f03457eed on Jul 1, 2023
12. fanquake referenced this in commit 56c05c5ec4 on Jul 17, 2023
13. fanquake referenced this in commit ff061fde18 on Jul 18, 2023
14. hebasto referenced this in commit 270d2b37b8 on Jul 21, 2023
15. jonasnick cross-referenced this on Jul 27, 2023 from issue Upstream PRs 1357, 1345, 1358, 1368, 1369, 1323, 1364, 1370, 1367, 1344, 1371, 1363, 1340, 1366, 1313, 1378, 1298, 1382, 1383, 1384, 1386 by jonasnick

Contributors
theStack real-or-random sipa

Labels
refactor/smell