MFC r351819: procstat/tests: Fix flakiness by waiting for program to start

Some of the procstat tests start a program "while1" and examine the process
using procstat, but did not wait properly for it to start (kill -0 will
succeed immediately after the child process has been created).

Instead, have "while1" write something when it starts, and use a fifo to
wait for that.

PR: 233587, 233588

MFC r346571,r346572:

Update the spelling of my name

Previous spellings of my name (NGie, Ngie) weren't my legal spelling. Use Enji
instead for clarity.

While here, remove "All Rights Reserved" from copyrights I "own".

MFC r318325:

Start writing up some basic feature tests for procstat

These tests query a running process for information related to the -b,
-c, -e, and -f flags; the -f testcase is largely stubbed out, pending
additional work to determine a good, deterministic descriptor.

Core file test support is coming soon--it requires a bit more effort
due to the fact that:
- coredumps can be disabled (kern.coredump=0).
- corefiles can be put in different directories than the current
directory, or be named something other than `<prog>.core`
(`kern.corefile`).

Start writing up some basic feature tests for procstat

These tests query a running process for information related to the -b,
-c, -e, and -f flags; the -f testcase is largely stubbed out, pending
additional work to determine a good, deterministic descriptor.

Core file test support is coming soon--it requires a bit more effort
due to the fact that:
- coredumps can be disabled (kern.coredump=0).
- corefiles can be put in different directories than the current
directory, or be named something other than `<prog>.core`
(`kern.corefile`).

MFC after: 2 months
Sponsored by: Dell EMC Isilon