implement PIN/passphrase generation UI

[inthewaves]

Closes GrapheneOS/os-issue-tracker#599

Passphrases have been implemented using EFF's Long Wordlist of $6^5$ words. In terms of entropy, an 8-word passphrase would have a search space of $(6^5)^8 \approx 2^{103}$. This wordlist can be easily changed; just make sure to update the various constants in the DicewareWordList class.

Test: Manual
Test: atest -c SettingsUnitTests:com.android.settings.password.generate (after building with m and running emulator)
Test: SetupWizard2:

adb shell pm enable app.grapheneos.setupwizard
adb shell settings put secure user_setup_complete 0
adb shell am start -a android.intent.action.MAIN -n app.grapheneos.setupwizard/app.grapheneos.setupwizard.view.activity.WelcomeActivity

[inthewaves]

Changes since rebase:

• fix PasswordComplexity parsing & remove flaky test functions
• allow skip and changing lock type from SetupWizard. I was reading a comment from BiometricUtil about how PIN is used by default, but I didn't realize it launched SetupLockPassword (via class function overrides) which has its own buttons for choosing lock and skipping. Should've compared it with the original SetupWizard flow
• clarify comments & test password lengths and selections

[inthewaves]

Changes since rebase:

• hide auto-PIN in SetupWizard and other fixes (auto-PIN originally disabled in SetupWizard but generation flow didn't handle that until now; see 4c8ad8f)
• make a copy of the credential in the save request for Fragment's SaveWorker