Directory parsing

This adds a directory summary tool, based off the files one, which summarises the amount of time spent in each directory. I'm a bit unfamiliar with BTreeMap and how it interacts with rayon, so I ended up cloning a couple of strings which seems like an inefficiency that someone more familiar with them might be able to help with 😺

Example output

❯ cargo run -- ../traces/pool.trace directories -s duration | head -n 50
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s                                                                                                                      [22/9541]
     Running `target/debug/strace-parser ../traces/pool.trace directories -s duration`

Directories accessed for files

      pid      dur (ms)       timestamp       directory name
  -------    ----------    ---------------    ---------------
   439489     14597.831    17:24:36.367978
   439489     14596.860    17:24:36.367978    .
   439489     14508.693    17:24:20.892514    ./refs
   439489     13099.752    17:24:20.849024    ./refs/remotes
   439489     12925.378    17:24:20.849024    ./refs/remotes/origin
   439489     11202.062    17:22:29.256390    ./refs/remotes/origin/environments
   439489      2803.811    17:11:09.703747    ./refs/remotes/origin/environments/production
   439489      1340.172    17:24:20.439701    ./refs/remotes/origin/merge-requests
   439489       182.465    17:17:26.665644    ./refs/remotes/origin/environments/staging
   439489        70.949    17:24:33.024496    ./objects
   439489        18.638    17:15:48.201167    ./refs/remotes/origin/environments/review-release-13-2ke04s
   439489        17.627    17:22:02.719233    ./refs/remotes/origin/environments/review-sm-invento-ouxvxi
   439489        16.610    17:14:23.956135    ./refs/remotes/origin/environments/review-release-13-ne30vp
   439489        12.597    17:14:10.194415    ./refs/remotes/origin/environments/review-dotcom-cat-2ch6ww
   439489        10.219    17:15:42.583203    ./refs/remotes/origin/environments/review-span-of-in-lgio2x
   439489        10.181    16:45:44.403715    ./refs/remotes/origin/heads
   439489         9.429    17:14:04.215349    ./refs/remotes/origin/environments/review-julia-lake-v7g6k6
   439489         9.250    17:12:17.020067    ./refs/remotes/origin/environments/review-whaber-oct-nurdra
   439489         9.086    17:22:23.380564    ./refs/remotes/origin/environments/review-5323-webpa-vqko7l
   439489         8.983    17:18:07.724842    ./refs/remotes/origin/environments/review-mw-netherl-km32fg
   439489         8.901    17:21:00.741301    ./refs/remotes/origin/environments/review-davis-town-z4xj86
   439489         8.722    16:47:26.552648    ./refs/remotes/origin/environments/review-eread-tw-r-15s0is
   439489         8.435    17:16:40.697419    ./refs/remotes/origin/environments/review-jarv-year-dqr7k8
   439489         8.354    17:11:19.224473    ./refs/remotes/origin/environments/review-marketing-iltmsc
   439489         7.541    17:14:12.841824    ./refs/remotes/origin/environments/review-patch-1982-f02a4t
   439489         7.524    17:17:52.386102    ./refs/remotes/origin/environments/review-aj-remove-u5m2x9
   439489         7.020    17:15:18.366408    ./refs/remotes/origin/environments/review-chart-impr-jspg2l
   439489         7.016    17:17:00.495284    ./refs/remotes/origin/environments/review-jyavorska-pe73sv
   439489         6.912    16:47:51.511106    ./refs/remotes/origin/environments/review-8684-publi-cedk4l
   439489         6.903    17:14:39.419611    ./refs/remotes/origin/environments/review-cg-handboo-83exgm
   439489         6.864    17:11:17.747917    ./refs/remotes/origin/environments/review-mops-hb-up-y0peg0
   439489         6.779    17:20:07.003150    ./refs/remotes/origin/environments/review-cfoster3-m-qzuq7j
   439489         6.695    17:17:41.122612    ./refs/remotes/origin/environments/review-dimitrieh-8v1z7z
   439489         6.605    17:20:51.701072    ./refs/remotes/origin/environments/review-patch-1982-2uw0jm
   439489         6.601    17:16:43.032100    ./refs/remotes/origin/environments/review-mops-hb-up-lta54g
   439489         6.541    16:47:31.036403    ./refs/remotes/origin/environments/review-manage-acc-0d0pu0
   439489         6.540    16:47:27.181698    ./refs/remotes/origin/environments/review-9184-creat-w52soc
   439489         6.521    16:47:44.521900    ./refs/remotes/origin/environments/review-record-ret-0bxz5i
   439489         6.478    17:16:44.856907    ./refs/remotes/origin/environments/review-mj-error-b-p1ayzv
   439489         6.444    16:47:28.657973    ./refs/remotes/origin/environments/review-jdbeaumont-izow9i
   439489         6.400    17:15:54.888981    ./refs/remotes/origin/environments/review-jc-ve-best-u6930d
   439489         6.343    17:18:41.940255    ./refs/remotes/origin/environments/review-navigation-mfq4e7
   439489         6.312    17:19:41.396049    ./refs/remotes/origin/environments/review-9171-commi-3c5t6a
   439489         6.298    17:15:02.157333    ./refs/remotes/origin/environments/review-ci-solutio-vdtjbc
   439489         6.176    17:19:49.259758    ./refs/remotes/origin/environments/review-update-pro-dksg2s