fix: implement robust file type checks to align with existing logic

[lrhan321]

Summary

Fix the compatibility issue mentioned in #17453 and #16203

Screenshots

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Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[laipz8200]

Hi @lrhan321, would you mind to add some tests for this PR?

[lrhan321]

I added some tests, but I'm not sure about the structure and file extension of the tool file. Please check and confirm whether to merge.

[lrhan321]

Now, strict validation of file types should only be performed when calling the workflow API and the input contains variables of file types.

[laipz8200]

LGTM