waddrmgr: remove direct references to BIP 44 in struct/variable names
waddrmgr: remove direct references to BIP 44 in struct/variable names

In this commit, we remove all direct references to BIP 44 as upcoming
changes will shift to a model that is no longer directly dependent on
BIP 44 in favor of restoring a layer of abstraction and allowing users
to manage multiple (purpose, coin type) scopes within the same
database.

Roasbeef/btcwallet,Roasbeef/btcwallet