[ONNX] Improve ONNX delegate quality (#32463)
### Details:
- *Support string constants*
- *Fix issue with opset version for `ai.onnx` domain*
- *Make frontend fail gracefully if file can't be read*
### Tickets:
- *CVS-175187*
Signed-off-by: Maxim Vafin <maxim.vafin@intel.com>
