feat: add Hall effect, ADC, and encoder counter sensor classes

[ninankh]

Summary

Adds the base sensor class along with three sensor driver implementations:

• DRV5056 Hall effect sensor
• ADS114S0x ADC sensor
• LS7366R Encoder counter sensor

Unit tests are included for the base class and all three drivers.

Changes

• base sensor class: shared interface/abstract methods used by the new sensor drivers
• hall effect sensor: driver implementation
• adc sensor: driver implementation
• encoder counter sensor: driver implementation
• Unit tests added for each of the above under tests/

Testing

• Added pytest coverage for all four modules
• Ran make test locally, all passing
• Ran make check for lint/format compliance

[codecov]

Codecov Report

❌ Patch coverage is 98.56115% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
opensourceleg/sensors/adc.py	98.3%	8 Missing and 1 partial ⚠️
opensourceleg/sensors/hall.py	98.4%	0 Missing and 1 partial ⚠️

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