When calling `erlfmt` with absolute paths for the files to format, the
excludes don't apply, even if the resolved paths of the excludes would
match the files to format.

Resolve the paths of the excludes based on the current working directory
and add them to the excludes.

This issue was observed when using the
[VS Code Erlang Formatter extension](https://marketplace.visualstudio.com/items?itemName=szTheory.erlang-formatter).
The extension invokes `rebar3 fmt` with the full path of the file to
format.

This handles Windows' `volumerelative` path types by properly resolving
them based on the "per-drive" working directory.

Also, resolve the input file absolute paths. This is new functionality;
if you were previously to use a file path like `a/../b`, that would have
been directly matched against the excludes. As a result, an exclude of
`b` would not have applied. This change makes sure relative path
resolution is consistent between `files`/`exclude_files`.

To avoid displaying different paths from what was requesting by config
or CLI options (e.g. when using the verbose flag), use a map of absolute
paths -> original paths and return the original paths from
`erlfmt_cli:set_difference/2` after applying excludes.