Add (mutable) type getters to edm4eic::vertex

The vertex object has a type object that is currently not rigorously defined. In the future it would be beneficial to have some concrete types that a vertex could be (e.g. primary, secondary, background, other...). Adding getters with bit shifting will allow for easier type identification, similar to that in `edm4hep::MCParticle`.

**Describe the solution you'd like**
Something similar to https://github.com/key4hep/EDM4hep/blob/main/edm4hep.yaml#L188-L220

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

Start by reading the edm4eic::vertex definition and comparing it with the referenced EDM4hep edm4hep.yaml lines 188-220. Clarify the concrete vertex-type values and their mutable bit-shifted representation before implementing the getters. Done means vertex type identification follows the agreed model and supports the proposed primary, secondary, background, and other categories.

Written by the indexing model from the issue text.