tests: Add test scenario for BME280 environmental sensor.

[nedseb]

Add a YAML test scenario file tests/scenarios/bme280.yaml for the BME280 driver.

Expected tests

• Mock: verify device ID register
• Hardware: read temperature, humidity, pressure
• Manual: validate displayed sensor values

Reference

• Driver: lib/bme280/
• Test framework: PR tests: add test framework with mock and hardware support. #28

Blocked by

• bme280: Add BME280 temperature, humidity and pressure sensor driver #9 — Driver must be implemented first.

[nedseb]

Already done: tests/scenarios/bme280.yaml exists with 39 mock tests and 6 hardware test scenarios, covering device ID, calibration parsing, compensated readings, mode transitions, configuration, and plausible range checks.