Optimize process command line computation
Optimize process command line computation

Summary:
Previously we computed the args and environment, then discarded the environment and joined the args together to make the command line. By cutting out all that extra work, we get a ~3% CPU win for a typical `processes` query.

Before:
```
 D:0  C:0  M:2  F:0  U:0  pack_processes_resources (1/5): duration: 0.592410087585 cpu_time: 0.053588293 memory: 12603392 fds: 4 utilization: 5.05
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (2/5): duration: 0.52742600441 cpu_time: 0.05227561 memory: 12578816 fds: 4 utilization: 4.95
 D:0  C:0  M:2  F:0  U:0  pack_processes_resources (3/5): duration: 0.524594068527 cpu_time: 0.052265788 memory: 12582912 fds: 4 utilization: 4.95
 D:0  C:0  M:2  F:0  U:0  pack_processes_resources (4/5): duration: 0.519255876541 cpu_time: 0.052351296 memory: 12697600 fds: 4 utilization: 5.0
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (5/5): duration: 0.525310993195 cpu_time: 0.05189243 memory: 12570624 fds: 4 utilization: 4.9
 D:0  C:0  M:2  F:0  U:0  pack_processes_resources   avg: duration: 0.537799406052 cpu_time: 0.0524746834 memory: 12606668.8 fds: 4.0 utilization: 4.97
```

After:
```
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (1/5): duration: 0.577349901199 cpu_time: 0.052007643 memory: 12525568 fds: 4 utilization: 4.9
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (2/5): duration: 0.516617059708 cpu_time: 0.050582555 memory: 12480512 fds: 4 utilization: 4.8
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (3/5): duration: 0.519332170486 cpu_time: 0.049710162 memory: 12492800 fds: 4 utilization: 4.7
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (4/5): duration: 0.523589849472 cpu_time: 0.051366226 memory: 12578816 fds: 4 utilization: 4.9
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources (5/5): duration: 0.528687000275 cpu_time: 0.049640225 memory: 12529664 fds: 4 utilization: 4.7
 D:0  C:0  M:1  F:0  U:0  pack_processes_resources   avg: duration: 0.533115196228 cpu_time: 0.0506613622 memory: 12521472.0 fds: 4.0 utilization: 4.8
```

(Adapted from https://github.com/facebook/osquery/pull/5200)

Reviewed By: guliashvili

Differential Revision: D13458612

fbshipit-source-id: 5642225a673f8ce954a60ec01fb7ddfcc79c0608

hackgnar/osquery,hackgnar/osquery,hackgnar/osquery