update NPU pipeline generate

[rnwang04]

Description

1. Why the change?

• Add timing logic to the generate function. When generate accepts do_print=True, print these timing information
• When we set max_new_tokens=32, now actually output 33 tokens, fix this issue
• transformer's generate actually return input_tokens + output_tokens, now we only return output_tokens, fix this issue

2. User API changes

No change.

3. Summary of the change

4. How to test?

• Unit test: Please manually trigger the PR Validation here by inputting the PR number (e.g., 1234). And paste your action link here once it has been successfully finished.
• Application test

[rnwang04]

PR validation is passed: https://github.com/intel-analytics/ipex-llm-workflow/actions/runs/11286182074