[QNN EP] Add support for GatherElements

[adrianlizarraga]

Description

• Adds support for the GatherElements operator to QNN EP.
• Adds GatherElements to QDQ quantizer tool.

Motivation and Context

Enable more models to run on QNN EP.

[adrianlizarraga]

@HectorSVC @jywu-msft I made this into a draft because of the many inconsistencies with the gather ops.

• QNN Gather ops do not support negative indices (supported by ONNX)
• QNN GatherElements output does not match ONNX or pyTorch when axis != 0
• QNN GatherNd output does not match ONNX when batch_dims != 0

These need to be addressed before this can be merged.