search.cc: improve UX for `nix search`

As proposed in #1634 the `nix search` command could use some
improvements. Initially 0413aeb35d6ee869a98b6565781c1cf47dc80080 added
some basic sorting behavior using `std::map`, a next step would be an
improvement of the output.

This patch includes the following changes:

* Use `$PAGER` for outputs with `RunPager` from `shared.hh`:
  The same behavior is defined for `nix-env --query`, furthermore it
  makes searching huge results way easier.

* Simplified result blocks:
  The new output is heavily inspired by the output from `nox`, the first
  line shows the attribute path and the derivaiton name
  (`attribute path (derivation name)`) and the description in the second
  line.

0 files changed, 0 insertions, 0 deletions