test/fuzz: collect and print Lua metrics

Fuzzing test for LuaJIT generates random Lua programs and executes them.
We want to build a fuzzing test that will produce Lua programs that will
not contain semantic errors and will trigger as much as possible
components in LuaJIT.

This proposed patch introduces metrics that gathered after running the
test. LuaJIT metrics gathered using LuaJIT getmetrics module [1]. All
gathered metrics test will output after running with a finite number of
runs or finite duration of time (options `-runs` and `-max_total_time`)
or after sending SIGUSR1 to a test process.

```
$ ./build/test/fuzz/luaL_loadbuffer/luaL_loadbuffer_fuzzer -runs=1000

<snipped>

Done 1000 runs in 1 second(s)
Total number of samples: 1000
Total number of samples with errors: 438 (43%)
Total number of samples with recorded traces: 87 (8%)
Total number of samples with snap restores: 30 (3%)
Total number of samples with abort traces: 55 (5%)
```

1. https://www.tarantool.io/en/doc/latest/reference/tooling/luajit_getmetrics/#getmetrics-c-api

NO_CHANGELOG=testing
NO_DOC=testing