onnxruntime

c97cc5c1 - Put all external project targets under the 'External' folder in VS (#21765)

Put all external project targets under the 'External' folder in VS (#21765) ### Description <!-- Describe your changes. --> Handle targets in subdirectories for external projects. All targets will now go in a per-project folder under 'External' e.g. gmock and gtest now get handled correctly and are under External/googletest vs. existing setup where they ended up as top-level projects.  ### Motivation and Context <!-- - Why is this change required? What problem does it solve? - If it fixes an open issue, please link to the issue here. --> Improve developer experience.