Layer-theta sampling fraction integration for e/gamma

[Dr-Stubborn]

BEGINRELEASENOTES
This pull request introduces a new Gaudi algorithm, SamplingFractionInLayerThetaTree, to the DetStudies package. The algorithm computes sampling fraction constants as a function of calorimeter layer and theta bin, and outputs detailed summary and event-level data in various ROOT formats. The implementation includes both the algorithm's source and header files, and updates the CMake configuration to link the required ROOT library.

New algorithm for calorimeter layer-theta sampling fraction analysis:

• Added SamplingFractionInLayerThetaTree Gaudi algorithm, which reads calorimeter hit collections, computes sampling fractions per (layer, theta) bin, and supports outputting results as event-level TTrees, summary TTrees, mergeable histograms, and a sf distribution for advanced analysis. [1] [2]
• The algorithm is highly configurable via Gaudi properties, supporting control over input/output collections, binning, and which outputs to produce.

Build system update:

• Updated Detector/DetStudies/CMakeLists.txt to link against ROOT::Tree, enabling the new algorithm to write ROOT TTrees.

ENDRELEASENOTES