debug: show output test when present with variablesReference

[connor4312]

Previously, if a DAP output event contained a variablesReference, we
would entirely ignore the output text in favor of shows its variables.
However, output can be richer than variable data: namely, it can show
ANSI sequences which would be inappropriate to format in
a variable value.

In this PR, if an output event has a single variable in its
variablesReference and output text, we show the output text instead
of the variable value. (Maybe we should also log output as plain text,
though this could be a confusing experience. I don't know of any DA's
that actually emit >1 variable in their output.)

For #172868
For #171732

(will need adoption in js-debug to actually fix those)

[roblourens]

One thing I noticed (which isn't new) is that the Process exited message shows up before other output, should I open an issue for that?

[roblourens]

Is this supposed to be colored now?

[connor4312]

Is this supposed to be colored now?

No, it need adoption in js-debug first. js-debug always sends an empty output string for variables, so you always see the old behavior.

One thing I noticed (which isn't new) is that the Process exited message shows up before other output, should I open an issue for that?

Yep, looks like an ordering bug in core. I'll fix that since I know where to look.

[connor4312]

Oh, nevermind. It is an ordering problem but I'm not sure it's core's thing to fix. The "process exited" is sent from the 'parent 'virtual' debug session, where the console logs are sent from the child session, so they are enqueued separately in core. Will have to think of the right way to deal with that, but that would also be fixed with microsoft/debug-adapter-protocol#85