generalize helper for loading module from source

[bowenliang123]

Description

• generalize module_import_helper for loading module from source
• it's used for avoid repeated code by
  • importing a module from the source file directly
    • Check, import and update the module name into sys.modules, according to Python docs Importing a source file directly
    • Support to use lazy import loader (disabled by default), which creates a real module object but is not loaded into memory, according to Implementing lazy imports. It may help to improve faster launch time and prevent actual loading unused modules (for LLM models, built-in tools, etc.), when it's turned on by default in the future.
  • getting subclasses of targeted parent type from the module

Type of Change

Please delete options that are not relevant.

• 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

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• TODO

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods
• optional I have made corresponding changes to the documentation
• optional I have added tests that prove my fix is effective or that my feature works
• optional New and existing unit tests pass locally with my changes

[takatost]

some err happened when module loading

[bowenliang123]

Tests added. Please review again.

[takatost]

LGTM