[llvm-dwarfdump][test] Add tests for dumping the .debug_line_str section.

This patch adds tests for dumping the .debug_line_str section. The
dumper of the debug_line_str section is able to write nonprintable
strings as escaped chars while the dumper of the debug_str and
debug_str.dwo sections cannot. I will fix them and add tests for them
in a follow-up patch.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D86916