REST: extend performance improvements to other parts of the API

REST: extend performance improvements to other parts of the API

We can trivially extend what we've just done to other parts of the API.

I haven't done much by way of benchmark but we're seeing multiple 'x's
pretty much across the board when filtering.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Stephen Finucane <stephen@that.guru>