android: implement biometric authentication (fingerprint)

[f321x]

Allows to unlock the android app with the android biometric api (e.g. fingerprint). Can be enabled in the settings. The initial version was LLM generated but i reviewed it and rewrote a couple things.

TODO: checkbox to enable it in the wizard during wallet setup once one password is enforced for creation of new wallets

closes https://github.com/spesmilo/electrum/issues/7560

[accumulator]

I assume this will be combined with #10339? (as handing over the wallet password to some biometric backend is a risk)

[f321x]

@accumulator no, the PRs are independent. The password is encrypted with a secret retrieved from the secure element inside the new Java activity, we then store the encrypted password in our config file, so the wallet password is not stored anywhere outside of Electrum.

[ecdsa]

this looks good to me, although I did not build an apk,

[f321x]

running this apk for 2 weeks now, no issues so far