Adjust target matching behaviour of repl and haddock commands

Normally a target like "pkg" does not select tests, benchmarks etc
(though this can be overridden by other configuration), but when a user
asks to repl/haddock "pkg:tests" then we should select tests
irrespective of defaults since that's the clear user intention.

This brings the repl and haddock commands into line with the build
command in this respect.