This has several benefits:
* Less abuse of `extra-sandbox-paths` Nix option
* Less inputs to the Android release build derivation
* Easier for users to sign the build themselves
* Simplification of `scripts/release-android.sh`
* Preparation for building using Nix Flakes
The only two remaining credentials passed via `extra-sandbox-paths` is
the Infura and OpenSea API keys, and there is no way around that other
than passing them via Nix arguments, but that would cause them to end up
in `/nix/store` as part of `.drv` files.
I'm also renaming `release-fdroid` to `build-fdroid` to be consistent.
Depends on: https://github.com/status-im/status-jenkins-lib/pull/42
Signed-off-by: Jakub Sokołowski <jakub@status.im>
