Drop Athena AMVF primary vertexing implementation
Remove deprecated Athena AMVF implementation InDetAdaptiveMultiPriVxFinderTool. Several legacy jobOptions were found to still reference this tool, without the new ACTS one. As they would need anyway to be migrated to CA configs, those are removed rather than introducing the ACTS AMVF configuration for legacy configs.
Also introducing option in config for ExperimentalActsIterativeFinding primary vertexing (keeping in mind this is known to be different from the Athena-based IVF)