test: add script to test all implementations

The script tests all implementations and prints PASS or FAIL status.
In case of failure it also prints implementation output to stderr.

This will be handy for adding new test samples.

Show test statuses and omit failing output:
```sh
$ ./test_all.sh 2>/dev/null
PASS artsiomkorzun
PASS baseline
PASS bjhara
PASS criccomini
FAIL ddimtirov
FAIL ebarlas
PASS filiphr
FAIL itaske
PASS khmarbaise
FAIL kuduwa-keshavram
FAIL lawrey
PASS padreati
FAIL palmr
PASS richardstartin
FAIL royvanrijn
FAIL seijikun
PASS spullara
PASS truelive
```

Show only passing implementations:
```
$ ./test_all.sh 2>/dev/null | grep PASS | cut -d' ' -f2
artsiomkorzun
baseline
bjhara
criccomini
filiphr
khmarbaise
padreati
richardstartin
spullara
truelive
```

For #61

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