MoreCast 2.0: Probability of precipitation

**As a** weather forecaster

**I need** a probability of precipitation attribute field

**So That** I can make a more informed decision regarding precipitation in my forecast

**Acceptance Criteria**
- [ ] Add a probability of precipitation attribute/spatial visualization from the ensemble weather models.

**Additional Context**
- The GEPS and GEFS are ensemble weather models available on SpotWx.com. I believe there is also an ensemble for the European model.

**Definition of Done**
https://github.com/bcgov/wps/wiki/Definition-of-Done

The issue names no files, entry points, or tests. Start by locating the existing ensemble weather-model integrations and the code that exposes spatial attributes and visualizations; done means a probability-of-precipitation attribute and spatial visualization are available from the GEPS and GEFS ensembles, with the European ensemble clarified if applicable.

Written by the indexing model from the issue text.