list of failures in groupby task

this issue will list failures (or timeout 2h+ of single script)

G1_1e9_2e0_0_0 - 1e9 rows, k=2 Finishes question 1 (run 1, 2) and question 2 (run 1, 2), prints head&tail of answers. As previously investigated it getting stuck (killed due timeout) before even starting question 3, due to R gc taking to much time. It probably could finish at some point but behaviour is not acceptable.
```
timed out after 7200s
```

G1_1e8_1e2_0_0, 1e8 rows, k=100 Finish q1-q9, out of memory during q10, reported in https://github.com/tidyverse/dplyr/issues/4334
```
Error: cannot allocate vector of size 762.9 Mb
```
G1_1e8_1e1_0_0, 1e8 rows, k=10 same
G1_1e8_2e0_0_0, 1e8 rows, k=2 same
G1_1e8_1e2_0_1, 1e9 rows, k=100, sorted same
G1_1e9_1e2_0_0, 1e9 rows, k=100 Finishes q1-q9, then killed by OS
G1_1e9_1e1_0_0, 1e9 rows, k=10 Finishes q1-q4, first run of q5, then timed out after 7200s
G1_1e9_2e0_0_0, 1e9 rows, k=2 Finishes q1-q2, then timed out after 7200s
G1_1e9_1e2_0_1, 1e9 rows, k=100, sorted Finishes q1-q9, then killed by OS

G1_1e9_1e2_0_0, 1e9 rows, k=100 Out of memory when reading data
```
MemoryError
```
G1_1e9_1e1_0_0, 1e9 rows, k=10 same
G1_1e9_2e0_0_0, 1e9 rows, k=2 same
G1_1e9_1e2_0_1, 1e9 rows, k=100, sorted same

G1_1e8_1e2_0_0 timeout on q8 or q10, reported https://github.com/h2oai/datatable/issues/1808, https://github.com/h2oai/datatable/issues/1541
G1_1e8_1e1_0_0 same
G1_1e8_1e2_0_1 same
G1_1e9_1e2_0_0 timeout on q8
G1_1e9_1e1_0_0 timeout on q3
G1_1e9_2e0_0_0 timeout on q3
G1_1e9_1e2_0_1 timeout on q8

G1_1e8_1e2_0_0, 1e8 rows, k=100 Finishes q1-q5, q6 (median) not yet implemented, getting killed by OS due to memory when doing q7
```
/bin/bash: line 1: 35402 Killed
```
G1_1e8_1e1_0_0, 1e8 rows, k=10 same
G1_1e8_1e2_0_1, 1e8 rows, k=100, sorted same
G1_1e9_1e2_0_0, 1e9 rows, k=100 Out of memory when reading data
```
MemoryError
```
G1_1e9_1e1_0_0, 1e9 rows, k=10 same
G1_1e9_2e0_0_0, 1e9 rows, k=2 same
G1_1e9_1e2_0_1, 1e9 rows, k=100, sorted same

G1_1e9_1e2_0_0, 1e9 rows, k=100 completed q1 and q2, before printing head&tail of q2 answer interrupted due to timeout 7200 seconds, error log:
```
signal (2): Interrupt
...
Allocations: 18881406001 (Pool: 18881383979; Big: 22022); GC: 14662
```
G1_1e9_1e1_0_0, 1e9 rows, k=10 same, during loading data
G1_1e9_2e0_0_0, 1e9 rows, k=2 same, during loading data
G1_1e9_1e2_0_1, 1e9 rows, k=100, sorted same, completing q1, q2, and run 1 of q3, before run 2 of q3 timeout

h2oai / db-benchmark