Adding an epoch to the 'steam' package

[Simon McVittie]

Before Valve's Steam game distribution platform became available on
Linux, the Debian source package name 'steam' was used by an unrelated
package sTeam, an "environment for cooperative knowledge managment"
(a wiki and related software). sTeam was removed from Debian in 2010,
and from Ubuntu in 2013. Valve's Steam was subsequently packaged for
Debian, also in 2013, reusing the 'steam' name.

sTeam had version numbers higher than Valve's Steam, and Launchpad is
stricter about monotonically increasing version numbers than dak is, so
Ubuntu added a 1: epoch to their 'steam' package when Valve's Steam
was introduced into Ubuntu.

This meant that the Ubuntu package superseded the native package
distributed by Valve, even if it was a lower version than Valve's, which
was needlessly confusing. As a result, Valve's native package now has the
same epoch as the Ubuntu package.

I would like to add the same 1: epoch to the steam package in Debian
and all of its binary packages, so that all of our version numbers
(Valve's, Debian's and Ubuntu's) are directly comparable again. This
would allow Ubuntu to sync the steam package from Debian unmodified,
if there are no functional changes that they need to make (at the moment
there are, but I intend to work on reducing or eliminating those during
the bookworm cycle).

As a side benefit from this, snapshot.debian.org would work properly again
(at the moment, it lists the historical sTeam as newer than Valve's Steam).

    smcv