feat: enhance comfyui workflow

[hjlarry]

Checklist:

Important

Please review the checklist below before submitting your pull request.

• Please open an issue before creating a PR or link to an existing issue
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Description

Change List

• use files instead of file, allow user upload multiple image files to do something like composite image layers in Comfy
• add a config field Image Node ID List can config the input images order
• add keywords replace prompt, user can pass dify's prompt to any nodes in Comfy
• use public method download of filemanager instead of private method _get_encoded_string
• update doc, PR: docs: update comfyui usage method dify-docs#348
• fix ComfyUI tool’s workflow encountered an error when running 'Failed to invoke tool: list index out of range' #10014

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

Testing Instructions

test locally

• Test A
• Test B