Disable lazy mode and promote torch.compile in CV MNIST example

[ZailiWang]

Description

Disable lazy mode and promote torch.compile in CV MNIST example

Type of changes

Please specify the type of changes, and delete the options that are not relevant.

• Documentation update
• Bug fix (changes which fix an issue)
• Others (please specify)

For lazy mode deprecation and torch.compile() promotion in examples.

Tests

Tested with the commands in the updated README.md.

Checklist

• I agree with the Developer Certificate of Origin.
• My code conforms to the following coding guidelines:
  • Use Python 3
  • Python code follows PEP 8 Coding Styles
• I have performed a self code review.
• I have made corresponding changes to the documentation.
• I have added tests that prove my fix is effective or that my feature works.