ptx: handle duplicate input files

[CrazyRoka]

Description:

Running ptx file file would only output the content of the file once. This caused the GNU test ptx ws.in ws.in | sort | uniq -u to fail (it expects identical output twice, which uniq -u filters out; we were outputting once, so uniq -u printed it).

Input files were stored in a HashMap keyed by filename. The second occurrence of the file overwrote the first.

Fix

Changed the internal FileMap storage to a Vec to preserve the order and multiplicity of input files.

Tests

• Some edge cases intests/ptx/ptx-overrun.sh are now passing correctly.
• Added regression test test_duplicate_input_files in tests/by-util/test_ptx.rs.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tty/tty-eof. tests/tty/tty-eof is passing on 'main'. Maybe you have to rebase?