[QNN EP] Enable QNN Saver for debugging issues (#17747)
### Description
- Enables option to use the QNN Saver backend for dumping QNN API calls
to file.
- Adds logic to read environment variable
`ORT_UNIT_TEST_ENABLE_QNN_SAVER` from QNN EP unit tests. If enabled,
unit tests will use the QNN Saver backend and dump files to
`./saver_output/`.
### Motivation and Context
QNN Saver makes it easier to debug issues when unit tests fail. The
output files generated by QNN Saver can be used to replay the exact QNN
API calls that lead to a specific error condition.
QNN Saver dumps QNN API calls (and weights) to disk.
- saver_output/saver_output.c: C file containing all QNN API calls.
- saver_output/params.bin: binary file containing all
input/output/parameter tensor data provided during tensor creation, op
config validation, and graph execution.
Enabling the QNN Saver backend has 2 note-worthy effects:
1. All QNN API calls will succeed.
2. Inference output returns dummy data.
Because the output files from QNN Saver are always overwritten, it is
recommended to run individual unit tests via the `--gtest_filter`
command-line option.
Example (linux):
```shell
$ ORT_UNIT_TEST_ENABLE_QNN_SAVER=1 ./onnxruntime_test_all --gtest_filter=QnnHTPBackendTests.Resize_DownSample_Linear_AlignCorners
```
