Testing: split ble encoder test (#2754)

test(sensors): Add mock encoder sensor

Add a new mock sensor driver for generating mock encoder sensor channel
data.

test(split): Add a peripheral sensor split test

Test BLE split logic for peripheral sensors (encoders).

app/tests/ble/split/peripheral-encoder/siblings.txt

@@ -0,0 +1,2 @@
+./ble_test_central.exe -d=2
+./tests_ble_split_peripheral-encoder_peripheral.exe -d=3