Add --summary option to print tests metrics

[lepapareil]

hurl version = 1.2.0

I write 4 test files, all 4 will succeed.

Currently I get:

$ hurl --output /dev/null /tmp/test*.hurl

What i expect using the new parameter --summary

$ hurl --output /dev/null --summary /tmp/test*.hurl
------------------------------------------------------
executed: 4
success: 4 (100%)
failed: 0 (0%)
execution time: 8000 ms
average time: 2000 ms
min time: 500 ms
max time: 3000 ms

I write 4 test files, 3 will succeed, 1 will fail.

Currently I get:

$ hurl --output /dev/null /tmp/test*.hurl
error: Assert Status
  --> /tmp/test2.hurl:2:10
   |
 2 | HTTP/1.1 302
   |          ^^^ actual value is <301>
   |

what i expect using the new parameter --summary

$ hurl --output /dev/null --summary /tmp/test*.hurl
error: Assert Status
  --> /tmp/test2.hurl:2:10
   |
 2 | HTTP/1.1 302
   |          ^^^ actual value is <301>
   |
------------------------------------------------------
executed: 4
success: 3 (75%)
failed: 1 (25%)
------------------------------------------------------
elapsed time: 4000 ms
average time: 1000 ms
min time: 500 ms
max time: 1500 ms
------------------------------------------------------