Allow users to directly send Hex in console downlink tool

[lytzV]

1. Are you using Helium hosted Console or running your own open source Console? Hosted

2. If you are on Helium hosted Console, which url are you currently on? This issue is observed across staging, prod and dedicated.

Please describe your issue:
Most device manuals have sample downlinks in hex format rather than base64 or utf-8. Currently, users often need to convert the hex payload to base64 or utf-8 format, and less tech-savvy users don't know how to do that and repeatedly use up customer success resources. Users should be able to directly use hex format in the console downlink tool.