feat(core): support custom dependency type internally

[hyf0]

Related issue (if exists)

#3051

Summary

• In most cases Cow<'static, str> would be &'static str behind, so clone would be not a problem.
• This also makes Rspack could support custom dependency type from the js side in the future.

🤖 Generated by Copilot at 22eff06

Added custom dependency types to rspack_core and refactored dependency and module logic. Changed dependency_type arguments to use clone instead of dereferencing to avoid copying.

Walkthrough

🤖 Generated by Copilot at 22eff06

• Add Custom variant to DependencyType enum and use borrow::Cow for string values (link, link, link)
• Update dependency_type field and arguments to use clone instead of dereferencing, since DependencyType is no longer Copy (link, link, link)
• Move normal_module_factory.rs to dependency/mod.rs and refactor dependency logic to separate module (link)