Include timing info in `@go.log_command` output

[mbland]

Should be relatively straightforward to add by replacing the default TIMEFORMAT from:

$'\nreal\t%3lR\nuser\t%3lU\nsys%3lS'

with something like this in @go.log_command_invoke:

TIMEFORMAT='real %3lR user %3lU sys %3lS'

to produce output something like this:

$time { sleep 1; echo 'Hello, World!'; }
Hello, World!
real 0m1.005s user 0m0.001s sys 0m0.002s

Then the timing info can be parsed in a similar fashion to the exit status.