[QNN EP] Fix support of ArgMin and ArgMax on all QNN backends (#16731)
### Description
- Fixes support for ArgMin/ArgMax to QNN CPU and HTP backends.
- Adds Q/DQ node unit selection logic.
- Handles casting int64 output to uint32 when necessary.
- Adds unit tests for ArgMax/ArgMin.
### Motivation and Context
QNN EP did not actually support ArgMin/ArgMax. Unit tests revealed that
the existing translation was not sufficient to support these ops.