Stop clobbering the collection of tickets stored in your session

Without this, things like Incident/Reply.html will stick the search for
IRs into your session, on top of a recent search you did. It also makes
the last search on your homepage your current session search.

However, we do need to update the session when showing search results,
so we'll keep the option of clobbering $session{'tickets'} around and
use it in Results.html.

This really just needs to reuse RT search infrastructure.

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For 2.9 this was originally done in 7e9cf5268.
This commit comes from a 2.6 branch, and ensures that CurrentSearchHash
isn't clobbered on every result display.
Nothing ever thaws the limits, so stop freezing.

This is incredibly old copied code.
/RTIR/Search/Results.html shows up less often

This reduces the number of tests we walk.  In 8d3cc5fa0f we stop adding
CurrentSearchHash on ever search rendering.  Since the menu code only
looks at CurrentSearchHash before showing a results link, it was
triggering even if there wasn't a tickets object in your session yet.

ShowResults now only update CurrentSearchHash when also updating
session{'tickets'}, rather than allowing session{'CurrentSearchHash'}
and session{'tickets'} to have nothing to do with each other.
Merge branch '2.9/stop-clobbering-session-collection' into 2.9-trunk