Stax Support

[chris124567]

Checklist

• App update process has been followed
• Target branch is develop
• Application version has been bumped

This PR:

• Adds Stax support
• Removes transaction streaming and instead loads transaction data up front in the case of signing a transaction
• Rewrites things according to the new guidelines

These changes have been reviewed here previously: SiaFoundation#3

[chris124567]

I did the SIA-02 (potential out of bounds write) and SIA-03 (blind signing enabled by default) changes requested in the audit. I made there be an option to enable hash signing which is disabled by default. I also fixed the errors in the APDU documentation, and replaced the tutorial with a link to our newer one which is much more detailed.

[tdejoigny-ledger]

Last comments (and we should be able to deploy the app):

• minor lint issue to fix
• I'm not a designer but the Stax icon/glyph could be improved (one for dashboard 32x32 and one for app 64x64)
  https://developers.ledger.com/docs/device-app/deliver/deliverables/icons#stax-template

[chris124567]

Fixed the linter issue and the icons look much better now!

[tdejoigny-ledger]

@chris124567
I merged too quickly, I didn't realize that the toml file wasn't updated with Stax, so the CI didn't pass, and there are still things to fix.
Please refer to #5