[XPU] Add XPU support for speculate_save_output_with_topk.

[Jiajun-Ji]

Motivation

Add XPU support for the speculate_save_output_with_topk op.
Integrate it into fastdeploy/spec_decode/mtp.py and fastdeploy/model_executor/xpu_pre_and_post_process.py.

Modifications

Usage or Command

Accuracy Tests

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@6d83dcc). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...tdeploy/model_executor/xpu_pre_and_post_process.py	0.00%	1 Missing ⚠️
fastdeploy/spec_decode/mtp.py	0.00%	1 Missing ⚠️

Additional details and impacted files

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  Files              ?      394           
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  Hits               ?    38542           
  Misses             ?    12525           
  Partials           ?     2770           

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