Qnn weight sharing improvement (#23945)
### Description
Qnn weight sharing improvement so that only the last session in the weight sharing group (the session that has both share_ep_contexts and stop_share_ep_contexts enabled) generates the .bin file. The .bin file name is decided from the 1st session. And all generated *_ctx.onnx models point to this single .bin to avoid post-processing work.
Previously each session generates a _ctx.onnx model with a .bin file. So it requires post-processing work to go through generated *_ctx.onnx models to get the last generated *_ctx.bin file and update all *_ctx.onnx to point to the same .bin file and remove the .bin files not used.
