fix(gcp): Update pricing_map to handle sku's for multiple regions

[Pokom]

Updates pricing_map to properly handle sku's with multiple regions. Previously we'd only consider the first region, but as detailed in #96 we're throwing away ~250 sku's that primarily impacted us-east1 pricing. There's two major changes:

1. Return a slice of parsed skus(1 per region in serviceRegion)
2. Add each of the parsed skus to the pricing map, instead of just one that's returned

• fixes #96