Fix rendering of logo-text with librsvg, make logo-text-version an alias for logo-text in testing/unstable

• logo-text.svg: Re-export based on logo-text-version.svg

  For whatever reason, rsvg-convert rendered the previous version of this SVG as blank. Copying the logo from logo-text-version.svg, deleting the version number 12, and adjusting the group hierarchy to minimize the diff seems to result in a logo that works as intended.

• Replace logo-text-version* with logo-text* equivalents in testing/unstable

  During the development cycle for a new Debian release, there is no version number that is applicable, so in contexts that would normally display the logo with distro name and version (such as gdm), use the version with only the distro name instead.

  Closes: #1086954

• Update changelog