Issue Description:

Currently, symbol kinds are parsed by comparing the kind string against a list of known symbol kinds, first as a whole and then with the first component discarded. However, this relies on the assumption that the first component of a symbol kind is a language identifier (e.g. `swift.func`). To prevent accidental loss of data, we should figure out a way to parse symbol kinds by taking their interface language into account.

The main problem here is the structure of the Decodable protocol: Each type's implementation is run in isolation, without taking into account the rest of the data being decoded. This will need to be handled somehow if we want to handle this.