Also includes a few improvements:
- Declare `bitcoin-wallet` as a provided binary for the qt package
(which has the wallet enabled).
- Use the `ninja install/strip` rule rather than installing each
component individually now that secp256k1 is no longer installed by
default.
- Reenable `ninja check` which is now fixed (used to segfault due to
setlocale).
Depends on D7305 and D7306.