Add random field multiply/square tests #955

1. 
   sipa commented at 11:35 pm on June 21, 2021: contributor

   Leverage the existing modmul256 function (which was added in #831, performing generic 256-bit modular multiplications) to test our fe_mul and fe_sqr functions.
2. Add random field multiply/square tests bdf19f105c
3. real-or-random approved
4. 
   real-or-random commented at 8:02 am on June 22, 2021: contributor

   ACK https://github.com/bitcoin-core/secp256k1/pull/955/commits/bdf19f105c64a48ae607304ea6483b3286093f24
5. 
   jonasnick commented at 5:40 pm on June 22, 2021: contributor

   ACK bdf19f105c64a48ae607304ea6483b3286093f24
6. jonasnick merged this on Jun 30, 2021
7. jonasnick closed this on Jun 30, 2021

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8. sipa referenced this in commit c020cbaa5c on Jul 14, 2021
9. apoelstra cross-referenced this on Jul 27, 2021 from issue Upstream PRs 879, 959, 955, 944, 951, 960, 844, 963, 965 by apoelstra
10. apoelstra referenced this in commit 196c993d1f on Jul 28, 2021
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Contributors
sipa real-or-random jonasnick