Remove entropy-protocol crate and move sign_and_encrypt module to entropy-client

[ameba23]

Since we are removing private mode i think we no longer need the entropy-protocol crate.

Anything in it which is needed by both a client and entropy-tss (eg: the hpke encryption stuff) should be moved to entropy-client, and anything which is only used by entropy-tss (eg: the protocol execution loop and Listener) should be moved to entropy-tss.

[ameba23]

Things which would move to entropy-client:

• RecoverableSignature
• KeyParams
• sign_and_encrypt - as well as the nodejs tests for it.

Everything else would move to entropy-tss::signing_client (which should really be renamed protocol_client).

The tricky bit will be the integration tests.