Shared :epp parsing used by both ErlangChunker and the call-graph extractor: parses a file in-process and filters out forms that originated in an -include'd header rather than the file itself.

:epp inlines the forms of every included file directly into the form list, marking file boundaries with {:attribute, _, :file, {Filename, _}} pseudo-forms. Each source file is processed independently elsewhere in the pipeline, so forms belonging to an included header are dropped here — otherwise a shared header's content would be duplicated (and have its text/line-numbers misattributed) under every file that includes it.