[llvm][TextAPI] add equality operator for InterfaceFile

This patch adds functionality to compare for the equality between `InterfaceFile`s based on attributes specific to linking.

Reviewed By: cishida, steven_wu

Differential Revision: https://reviews.llvm.org/D96629

GitOrigin-RevId: eb2eeeb76f7a294b2a8ddd6d09aafe1402ed9348
6 files changed