feat(wallet_ffi): new ffi method to create output features (fixed flag size for dibbler)

[mrnaveira]

Description

• Created a new FFI method to create an output features object, by passing the byte values as parameters.
• I decided to not expose the DAN layer features, as they are most likely going to change and also would require exposing more struct definitions.
• Updated the C header with the definition of the new method

Motivation and Context

Currently the mobile apps cannot properly import faucet UTXOs, as they are passing null values for output features and covenants to the wallet_import_external_utxo_as_non_rewindable method, which is not allowed. So the mobile apps needs new FFI methods to create both output features and covenants. This pull request deals with output features only.

This PR is an adaptation due to the output flags size, as the original PR was done over development which has consensus breaking changes (flag size was increased from 1 byte to 2 bytes).

How Has This Been Tested?

Created two new unit tests for the new FFI method