Simplify Avionics Shell (UARTCommandHandler)

[Elan456]

Description

Summary of Changes

• Add more testing hooks for analog voltage reading in HAL
• Removal of command history in Avionics Shell
• Modularization of input handling in the Avionics Shell

Motivation

Make the codebase easier to maintain, test, and extend, while removing unused or overly complex features.
The UARTCommandHandler was utilizing dynamic memory for the command history, so it's good to eliminate that until it can be re-implemented with a static allocation.

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Testing

Tested by opening a shell on MARTHA 1.4 and ensuring most things work right

Check all that apply:

• I have added or modified tests to cover these changes.
• I have manually tested the changes on the target device(s) or environment(s).
• Existing tests were reviewed to ensure they still work as expected.
• If tests were not added or modified, explain why:

  (Provide reasoning here)

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Building

• This change successfully builds in at least one of the following environments:
  • Native repo
  • Target device(s) (e.g., MARTHA)
• If the build fails in any environment, explain why:

  (Provide reasoning here)

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Checklist

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code where necessary for clarity.
• I have made corresponding updates to documentation (if applicable).

[Jshepherd06]

looks good