Support running grunt phpunit tasks inside Vagrant environments

[netweb]

Via @ocean90 in ticket:35557#comment:22

It would be awesome if the phpunit task would run in Vagrant, see ​https://github.com/xwp/wp-dev-lib/blob/f95a6e9e60fc261af655be929cee637e93149f41/check-diff.sh#L532-L552. :-)

Currently if your not SSH'd inside the Vagrant environment and working on files locally on the operating system side (not inside the virtual machine) then the grunt phpunit tasks will fail.

We should use something similar to the xwp/wp-dev-lib code linked above so that if a Vagrant environment is detected then the grunt phpunit and default, ajax, multisite, and external-http sub tasks and configurations will be passed through via SSH to inside the Vagrant environment.

[desrosj]

With the introduction of the local Docker environment (which is included in trunk and does not require using an external tool), I'm of the opinion that we should instead switch this to run within the Docker container.

Adding a close suggestion. Happy to open a new ticket for exploring that route instead.

[JeffPaul]

While I like having multiple tools supported here, I agree that the primary focus from core should like be the local Docker env and that closing this seems reasonable.