fix: respect telescope's path_display

[delphinus]

fix #47

Now path_display can be specified by these priorities.

1. Option specified with the command or Lua code.
   - :Telescope frecency path_display={"absolute"}.
   - or :lua require("telescope").extensions.frecency.frecency { path_display = { "absolute" } }.

2. opts.extensions.frecency.path_display in setup.

3. opts.defaults.path_display in setup.

   require("telescope").setup {
     defaults = {
       -- This has the 3rd precedence.
       path_display = { "absolute" },
     },
     extensions = {
       frecency = {
         -- This has the 2nd precedence.
         path_display = { "shorten" },
       },
     },
   }