Enforce configured decoder

Changes

• Ensure configured blackbox-decode is used consistently

Installation:

• Download the archive (from assets) for your operating system
• Expand the archive (File Manager, tar, unzip, 7zip as preferred)
• Copy the executable files somewhere convenient
• Make sure you also have inav's blackbox_decode installed and on $PATH / %PATH% or set by configuration.

Manual:

User Guide and installation instructions