Add NewDirectIOWithTerminal

[ehazlett]

This adds NewDirectIOWithTerminal as well as a test for PTY (TestContainerPTY) to test that output has control codes.

Refs: #2307

[dmcgowan]

LGTM

[crosbymichael]

I think this needs a direct.Wait() or close to fix the race. You can test locally with go test -c -race

[dmcgowan]

The tests failed with a data race, but not quite sure I understand what is racing though. Restarted but captured the race stack in this gist https://gist.github.com/dmcgowan/674b2dd6c3dfcce3fe54b565f5ce1ba2

[crosbymichael]

@dmcgowan io will race if you try to read from the buffer if the process hasn't finished flushing

[ehazlett]

@dmcgowan thanks for the gist. i've updated to fix the race. thx!

[codecov-io]

Codecov Report

Merging #2310 into master will decrease coverage by 0.02%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #2310      +/-   ##
==========================================
- Coverage   45.54%   45.51%   -0.03%     
==========================================
  Files          83       83              
  Lines        9185     9190       +5     
==========================================
  Hits         4183     4183              
- Misses       4326     4331       +5     
  Partials      676      676

Flag	Coverage Δ
#linux	50.04% <0%> (-0.04%)	⬇️
#windows	41.24% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
cio/io_unix.go	70.65% <0%> (-4.07%)	⬇️

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[crosbymichael]

LGTM

[dmcgowan]

Found this PR introduces a bug. Clients which were calling NewDirectIO before and had Terminal set correctly, will not have Terminal overwritten to false. The solution would be have NewDirectIO use the Terminal value instead of false, or get rid of the WithTerminal option have the caller set the fifo Terminal value before calling NewDirectIO