Bump min Node.js version to 22 (i.e. drop Node 20 and 21)

[webmaster128]

At some point in H1 2026 we will want to drop Node 20 support. Not urgent but this unlocks a few things.

• [ ] https://github.com/cosmos/cosmjs/issues/1810
• [ ] @scure/bip39 2.0 is an ESM package with dependencies, and Yarn 4's import loader hooks are compatible with node 22+, not node 20, so there's an error in the node 20 CI. Same trouble as at https://github.com/cosmos/cosmjs/pull/1804 from https://github.com/cosmos/cosmjs/pull/1843
• [ ] Remove hash-wasm dependency and just use JS implementation from @noble/hashes