feat(ads1x15): update to use pure read function

[finger563]

Description

• feat(ads1x15): update to use pure read function and protect internal read_two function with mutex to make API more consistent with the other analog expander classes
• Update affected examples (ads1x15 and controller)
• Rebuild docs

Motivation and Context

Allows the use of the same read/write functions across the analog expander classes currently offered (Ads1x15, Ads7138, Tla2528).

How has this been tested?

Building the ads1x15 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.