Support cluster 0x0408 Soil Moisture (TZ-1288)

[dmage]

Is your feature request related to a problem?

It seems it's impossible to have the soil moisture cluster with the existing SDK. There is already support for 0x0405 Relative Humidity (humidity_meas), which should have exactly the same implementation, but with a different ID.

Describe the solution you'd like.

A new API (soil_moisture) that'll be a copy of humidity_meas, but with ID 0x0408.

Describe alternatives you've considered.

I tried to create a custom cluster via esp_zb_zcl_attr_list_create(0x0408), but it isn't accepted by esp_zb_cluster_list_add_custom_cluster (it returns ESP_ERR_INVALID_ARG).

Additional context.

No response