deprecating bip39 & bip32 code

[dynst]

What about undoing #966?

Now that a stronger (and less bloated?) dependency ecosystem exists, seems like most of this code could just be replaced with @scure/bip39 and @scure/bip32, especially after migrating #1272.

[webmaster128]

#966 was conceptually reverted in #1843 using @scure/bip39 instead of our own implementation. Less code to audit for sure but otherwise no change for users. The slip10 implementation remains as-is as discussed in #1856.

Thanks!