v0.9.0: Passive slashing, per-output type, better setup and debug experience

Major changes since v0.8.1

Pre-images are now used to generate block signatures

Block signatures are now based on pre-images for the "signature noise" derivation.
This implements one of the aspect of Agora's passive slashing policy,
which is that signing two blocks for the same height reveal a validator's private key.

Transaction type has been moved to Output

Previously, transactions had a "type" field that would indicate the type of its output:
payment (the default), freeze, or coinbase. This created issues as payment and freeze
needed to be mixed (e.g. to avoid creating a refund transaction that was frozen).
The type field is now part of the Output, and may be extended in the future.

Multiple Talos (setup interface) bug fixes

The setup interface had a few issues, where some field would be empty when
run in a particular way, making navigating between menus impossible.
Those issues have been fixed and the interface now works as expected on all devices.

Agora will now dynamically export its symbol

Agora now use the export-dynamic linker option by default, which should result
in proper stack traces on Alpine Linux (and potentially other platforms),
at the cost of slightly bigger binary. Stripping the binary will still work.