builtin/ls-files: stop using `the_repository`

builtin/ls-files: stop using `the_repository`

Remove the_repository global variable in favor of the repository
argument that gets passed in "builtin/ls-files.c".

When `-h` is passed to the command outside a Git repository, the
`run_builtin()` will call the `cmd_ls_files()` function with `repo` set
to NULL and then early in the function, `show_usage_with_options_if_asked()`
call will give the options help and exit.

Pass the repository available in the calling context to both
`expand_objectsize()` and `show_ru_info()` to remove their
dependency on the global `the_repository` variable.

Mentored-by: Christian Couder <redacted>
Signed-off-by: Usman Akinyemi <redacted>
Signed-off-by: Junio C Hamano <redacted>