Add libde265 decoder smoke test

Changes:

• d/t/*: add decoder autopkgtest (Closes: 1052214).

Testing:

• run build and autopkgtest using PPA (ppa:vpa1977/libheif)[1]
  • package builds:
    • https://launchpad.net/~vpa1977/+archive/ubuntu/libheif/+sourcepub/15164744/+listing-archive-extra
  • autopkgtest pass:
    • amd64
    • arm64
    • armhf
    • i386
    • ppc64el
    • s390x

Video file attribution:

• the sample was produced for this test and does not need any license changes.

[1] https://launchpad.net/~vpa1977/+archive/ubuntu/libheif