Feature: `brew ls --taps`

This option to the `ls` command shows the source of the installed formulae. If a formula is included in the core repository, just print the name.  If the formula is installed from a tapped repository, print user/repo/name:
```
$ brew ls|grep numpy
numpy
$ brew ls --taps|grep numpy
homebrew/python/numpy
```
Sufficiently fixes #29586.