Bring in EDK2 routines for printing and parsing device paths.

This commit implements the (mostly?) Linux compatible
efidp_format_device_path and efidp_parse_device_path APIs. These are
the only APIs exposed through this library. However, they are built on
code from Tianocore's EDK2 MdePkg. They are brought in as new files
here for reasons described in FreeBSD-update.

Symbol versioning will be introduced to control what's exported from
the EDK2 code.

Some structural changes may be necessary when we move to sharing with
sys/boot/efi.

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