[largeNbDicts] Print more metrics into csv file

[largeNbDicts] Print more metrics into csv file

Summary:
Add column headers and data for whether it's a compression or a decompression
run, compression level, nbDicts and dictAttachPref in additional to
compr/decompr speed.

Test Plan:
Example output:

```
./largeNbDicts
Compression/Decompression,Level,nbDicts,dictAttachPref,Speed
Compression,1,1,0,300.9
Compression,1,1,1,296.4
Compression,1,1,2,307.8
Compression,1,10,0,292.3
Compression,1,100,0,293.3
Compression,3,110,0,106.0
Decompression,-1,110,-1,155.6
Decompression,-1,110,-1,709.4
Decompression,-1,120,-1,709.1
Decompression,-1,120,-1,734.6
```