adding in to physlite an extra container with sihit electrons

As discussed at AMG meeting 8-12-2023, this MR is adding SiHit electrons to PhysLite to allow Higgs to four lepton to evaluate the electron background in PhysLite. This is the last missing feature for the H4l group before migrating to PhysLite. SiHit electrons are written to a separate container. The increase in PhysLite size is minimized by suppressing the cluster and track, and replacing them with decorations for the required information. Care has been taken to avoid including the standard LooseLH electrons as well as any additional FSR electron close to muons - both of these pass the simple SiHit selection. As well, SiHit electrons are only kept for events with a pair of muons or electrons with the minimal selection. The increase on the ttbar sample is seen to be 1.6% - @elmsheus will need to adjust the size checks for the CI. Note that this size increase is about 1/2 of that expected without the requirement of a pair of leptons. Further reduction may eventually be obtained by adding in bit compression in a future step.