fix: make testing more verbose with -stats (fixes #12)

[1ethanhansen]

No description provided.

[1ethanhansen]

@ee7 much more verbose now!

[ee7]

LGTM.

To others: from the upstream docs:

v -stats file_test.v - this will run the test_ functions, and show a report about how much time it took to run each of them too.

CI log before:

Checking grade_school exercise...
Checking grains exercise...

CI log after:

Checking grade_school exercise...
---- Testing... ----------------------------------------------------------------
--------------------------------------------------------------------------------
running tests in: /home/runner/work/vlang/vlang/temp/run_test.v
     OK    [ 1/18]     0.003 ms     1 assert  | main.test_empty_roster()
     OK    [ 2/18]     0.008 ms     1 assert  | main.test_roster_one_person()
     OK    [ 3/18]     0.009 ms     1 assert  | main.test_roster_three_people()
     OK    [ 4/18]     0.006 ms     1 assert  | main.test_roster_duplicate_in_same_grade()
--------------------------------------------------------------------------------
     OK    [ [5](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:6)/18]     0.005 ms     1 assert  | main.test_cant_have_one_person_in_two_grades()
     OK    [ [6](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:7)/18]     0.003 ms     1 assert  | main.test_just_one_person_duplicated()
     OK    [ [7](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:8)/1[8](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:9)]     0.005 ms     1 assert  | main.test_students_added_to_multiple_grades()
     OK    [ 8/18]     0.013 ms     1 assert  | main.test_adding_same_student_multiple_grades()
     OK    [ [9](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:10)/18]     0.003 ms     1 assert  | main.test_just_one_person_multiple_grades()
     OK    [[10](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:11)/18]     0.009 ms     1 assert  | main.test_students_sorted_by_grade()
     OK    [[11](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:12)/18]     0.006 ms     1 assert  | main.test_students_sorted_by_name()
     OK    [[12](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:13)/18]     0.021 ms     1 assert  | main.test_students_sorted_by_grade_then_name()
     OK    [[13](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:14)/18]     0.001 ms     1 assert  | main.test_grade_empty_if_no_students_overall()
     OK    [[14](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:15)/18]     0.007 ms     1 assert  | main.test_grade_empty_if_no_students_in_that_grade()
     OK    [[15](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:16)/18]     0.006 ms     1 assert  | main.test_adding_same_student_twice_just_query_grade()
     OK    [[16](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:17)/18]     0.007 ms     1 assert  | main.test_adding_same_student_two_grades_just_query_grade_2()
     OK    [[17](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:18)/[18](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:19)]     0.005 ms     1 assert  | main.test_adding_same_student_two_grades_just_query_grade_3()
     OK    [18/18]     0.007 ms     1 assert  | main.test_students_sorted_by_name_in_grade()
     Summary for running V tests in "run_test.v": 18 passed, 18 total. Runtime: 0 ms.

        V  source  code size:      22716 lines,     613590 bytes
generated  target  code size:      22143 lines,     769000 bytes
compilation took: 313.3[20](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:21) ms, compilation speed: 72500 vlines/s
Summary for all V _test.v files: 1 passed, 1 total. Runtime: 3[22](https://github.com/exercism/vlang/actions/runs/3772486477/jobs/6413447232#step:4:23) ms, on 1 job.

Checking grains exercise...