[CHIA-1128] Generalize Keychain to support multiple key types

[Quexington]

With the advent of vaults, in order to preserve existing UX where the wallet can perform all actions by itself, you need a secp private key available to the wallet. In order to store these private keys in the keychain, this PR generalizes the keychain code to support keys of any type.

[github-actions]

File	Coverage	Missing Lines
chia/cmds/keys.py	40.0%	lines 339-340, 394-395, 475-476
chia/cmds/keys_funcs.py	89.7%	lines 325-326, 331
chia/cmds/sim_funcs.py	0.0%	lines 38-39, 155-157, 184
chia/farmer/farmer.py	83.3%	lines 237
chia/plotting/check_plots.py	0.0%	lines 11
chia/plotting/create_plots.py	33.3%	lines 99, 105, 109, 114, 118-119
chia/util/keychain.py	97.1%	lines 425, 574
chia/wallet/wallet_node.py	94.7%	lines 450

Total	Missing	Coverage
238 lines	26 lines	89%