vndk-def: Add deps-unresolved command

This commit adds deps-unresolved subcommand.  This subcommand will print
unresolved DT_NEEDED entries or unresolved symbols of the ELF file with
matching path.  This command can help the GSI debug process.

Test: python3 vndk_definition_tool.py deps-unresolved \
--system "${GSI}/system" --vendor "${DEVICE}/vendor" \
--path-filter "/vendor/.*"

Change-Id: If0a4acb495dacfbcd62f58abed7dc6db1618e8a3