Lep+track vertexing for VSI

Hello,

This MR adds an 'all (non-electron) ID + GSF from electrons' tracks seeding option to VSI. This is useful in reconstructing lepton+track kind of secondary vertices, especially useful for the displaced HNL search. Another JO added is a final skimming to remove any secondary vertex without a lepton track attached to it. This is useful mainly to reduce the size of the output collection (removes trk+trk kinds of vertices).

The goal would be to later use these JOs to add an extra SV container to DAOD_LLP1 (will be added in another MR).

Cheers, Sagar

Tagging @jburzyns and @gfrattar to take a look as TVPD conveners.