firmware: recover slow BNO086 startup

tests/test_xiao_sensor_node_contract.py

@@ -35,6 +35,9 @@ def test_imu_uses_verified_i2c_address():
     imu = source("imu.cpp")
     assert "BNO086_I2C_ADDRESS 0x4B" in config
     assert "findBnoAddress" not in imu
+    assert "BNO086_INIT_ATTEMPTS" in imu
+    assert "BNO086_RUNTIME_RETRY_MS" in imu
+    assert "bno086.wasReset()" in imu
 
 def test_gps_uses_verified_uart_baud():
     config = source("sensor_node_config.h")