Add Telemetry Hex Storage Format

[cnalley]

This PR adds a hex format telemetry log entry. The log entry is fixed width hexadecimal and contains the entire contents of the telemetry packet struct. This format can be used with the telemetry plotter here https://github.com/cnalley/telemetry-plotter. Some additional placeholders were also added for future output formats. The existing csv format only saves the data member of the telemetry struct while the new hex format saves the entire telemetry packet. The two new placeholders would in the future provide a hex format to save just the data member of the telemetry packet struct and a csv format for the complete telemetry packet. These new formats would open up additional configuration options for klog to leave all telemetry logs in the same file (if it's a complete telemetry packet for later decoding) or just the data member if each telemetry source is saved to individual files with distinct file names.

[davesims]

:wave: Hey there @cnalley, nice to see you! Thanks for the PR, we'll have a look.