Link Inspector from file details view

[Trighap52]

Closes #19032

Summary

• add an Inspector link to the project file details metadata section
• use the same inspector URL pattern already used in admin release detail
• add a functional test to verify the inspector link is rendered for a release file

Testing

• T=tests/functional/test_project.py make tests

[woodruffw]

I'll let the actual maintainers opine, but I don't think there was consensus in #19032 about this being something that PyPI wants to formally expose in the UI -- the inspector is a debugging tool and exposing it directly in PyPI's UI may mislead users about it being a first-class feature of PyPI itself.