Sgl/flex porting

Fix the txmaker test util

This option allows to compile the testnet app in a mode that allows
autoapproving any request, in order to measure the performance of
various operations either in speculos, or on a real device.

These tests are no longer worth the maintenance burden, as they test specific conditions and
only apply to an old version of the app protocol.
The corresponding tests for the newer version of the protocol are kept in the codebase.

It is useful to test that large amounts are shown correctly; instead of generating the psbt
synthetically, we hardcode a fixed psbt so we can hardcode the screenshots.

Performance test suite

… using a hardcoded binary

…Nano S; default to 'nanosp' in tests

Co-authored-by: François Beutin <101576048+fbeutin-ledger@users.noreply.github.com>

Remove Nano S target

…y_external_outputs functions

…using NBGL.

If a transaction has only a single non-change output, then we can fit the
"Amount", "To" and "Fees" fields in a single screen.

By caching the first few external outputs during output preprocessing, we can greatly
simplify the handling of the swap-related code, and the simplified UX for a single
external output.

This also allows to move all the swap-related checks in a single function.
Finally, by moving all the checks not related to user approval out of show_alerts
and display_output, we can omit calling these functions at all during swaps.

… transaction flow on flex/stax

Various simplifications in the code to generate the ragger instructions.

…tead of waiting for the timeout

… remaining flows to use 'accounts' instead of 'wallet policy'

Minor adjustments needed in some tests as the page splitting changed.

Refactoring and Stax UX revamp