Add Direct Boot support so SpeakTouch can be used before the initial unlock

[PatrykMis]

More information:

• https://developer.android.com/training/articles/direct-boot
• https://github.com/GrapheneOS/platform_packages_apps_Updater is a trivial example of using this.

We need to mark a subset of the functionality as direct boot aware and make sure it's capable of running in that state. A minimal amount of data needs to be migrated to being stored in device encrypted storage via the APIs for this. No sensitive user data should be marked that way. The SpeakTouch settings and other configuration is what's expected to be there. There shouldn't be any kind of history, speech dictionaries, stats or other sensitive data in device encrypted storage though.

We shouldn't also forget to handle special case while the selected TTS does not have direct boot support, then SpeakTouch should switch to supporting while the time of boot_locked.