Feature/richie/serial data downloader

[cowsed]

This closes #237

Description

Added a Serial transport layer for the Flight Data Dumper
Added firmware code for enabling a special shell command for dumping data in base64 over the serial connection

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Added the configuration CONFIG_F_CORE_BASE64_DATA_DUMP_SHELL=y to the datalogger sample. Used FDD with port of /dev/pts/X to download data

Test Configuration:

Checklist:

• New functionality is documented in the necessary spots (i.e new functions documented in the header (If theres no header do i not have to document 🤔 )
• The CI checks are passing
• I reviewed my own code in the GitHub diff and am sure that each change is intentional
• I feel comfortable about this code flying in a rocket