Update secp256k1 library

[jacogr]

Closes #294
Closes #307

Some stats -

• previous build
  • 344,384 -> 171,586 (49.82%)
  • https://github.com/polkadot-js/wasm/runs/5660851129?check_suite_focus=true#step:3:438
• this branch
  • 340,174 -> 171,464 (50.40%)
  • https://github.com/polkadot-js/wasm/runs/5673377568?check_suite_focus=true#step:3:409

[jacogr]

Have some small issue on my M1 locally though, although CI works, see rust-bitcoin/rust-secp256k1#283

[polkadot-js-bot]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.