Feat/ads7138 delayed init

[finger563]

Description

• Store Config in Ads7138 class
• Add initialize() function which calls protected init(config_)
• Update Config to have auto_init bool (default=true)
• Only call initialize() in constructor if config.auto_init is true

Motivation and Context

Sometimes (e.g. when you control power to various chips on the bus to enable ultra-low power modes for your device) you need to be able to separate the class construction from the device initialization. This PR adds support for that, enabling the user to both delay initialization if they choose to do so, as well as to call initialize() whenever they want (e.g. after power cycling the bus).

How has this been tested?

Building the example.

Screenshots (if appropriate, e.g. schematic, board, console logs, lab pictures):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Hardware (schematic, board, system design) change
• Software change

Checklist:

• My change requires a change to the documentation.
• I have added / updated the documentation related to this change via either README or WIKI

Software

• I have added tests to cover my changes.
• I have updated the .github/workflows/build.yml file to add my new test to the automated cloud build github action.
• All new and existing tests passed.
• My code follows the code style of this project.