Move packages to gz and add ignition alias

[chapulina]

• Part of Debian packages from ignition to gz gazebo-tooling/release-tools#736
• Uses a modified version of the script in: Add script to rename packages from ignition to gazebo gazebo-tooling/release-tools#726

Test build:

Conflicting with old ignition nightlies

Get:1 http://packages.osrfoundation.org/gazebo/ubuntu-nightly focal/main amd64 libignition-gazebo7-dev all 6.999.999+nightly+git20220630+1rcb61c01f8894e4f435f544d3511f346eaa753142-1~focal [1,620 B]
Fetched 1,620 B in 0s (4,545 B/s)                   
(Reading database ... 477666 files and directories currently installed.)
Preparing to unpack .../libgz-sim7_6.999.999+nightly+git20220630+1rcb61c01f8894e4f435f544d3511f346eaa753142-1~focal_amd64.deb ...
Unpacking libgz-sim7:amd64 (6.999.999+nightly+git20220630+1rcb61c01f8894e4f435f544d3511f346eaa753142-1~focal) ...
dpkg: error processing archive /var/cache/apt/archives/libgz-sim7_6.999.999+nightly+git20220630+1rcb61c01f8894e4f435f544d3511f346eaa753142-1
~focal_amd64.deb (--unpack):
 trying to overwrite '/usr/lib/x86_64-linux-gnu/libgz-sim7-ackermann-steering-system.so.7.0.0~pre1', which is also in package libignition-ga
zebo7:amd64 6.999.999+nightly+git20220629+1rcb61c01f8894e4f435f544d3511f346eaa753142-1~focal
dpkg-deb: error: paste subprocess was killed by signal (Broken pipe)

Test build after fcc40ca:

After 5c47c4b:

[chapulina]

Locally able to install new debs on top of old ones 🎉