fix(filesystem): fix numerous problems with searching

[cseickel]

fixes #806

This fixes #806 by inserting the user supplied find args at the right location.

It also refactors cancelling of search jobs in a safe way, and manages the limit better by only counting the result if the
score is > 0. Also, once the limit is reached, it cancels the external search job (which is fd or find).

Using these args in my personal config, I can now do a fuzzy search from root and actually find a file in a reasonable
amount of time:

  find_args = {
    fd = {
      "--exclude",
      ".git",
      "--exclude",
      "node_modules",
      "--exclude",
      "/sys",
      "--exclude",
      "/proc",
      "--exclude",
      "/tmp",
    },
  }