Package / SONAME change for libcamera 0.7.1 backport

Hi!

I'm preparing a trixie backport of libcamera 0.7.1 bringing better
hardware support, performance improvements and bug fixes. libcamera
still changes SONAME regularly (typically with major versions), so
just like in sid and in the previous libcamera 0.5 backport, this
will require updating the package name and:
- a visit to the backports NEW queue
- a rebuild in backports of reverse dependencies, fortunately that's
  just pipewire

Best,