We have a C API, but (internal) C++ template instantiations are visible
and so get flagged by `dpkg-gensymbols`. This change ignores the one
use of C++ by marking it optional. This is listed as a usage scenario
in the dpkg-gensymbols man page.
Note this requires a change how we call dpkg-gensymbols: if the `-O`
parameter is specified, the file is not treated as being a template file
(see man deb-src-symbols) and so the tags are not interpreted.
Additionally the file gets overwritten with the non-tag version. So this
change removes the `-O` parameter, and changes the archiving of the
generated file.
This change adds additional checks for the symbols file:
- if a line with a method name gets changed, the package version number
in that line also needs to be updated
- for major API changes (methods renamed or removed) the API version
numbers needs to be incremented
- the API version numbers in the .symbols file and in `CORE_API_VERSION.md`
need to match
This enhances the packaging GHA to be able to verify the renamed
core library. Since the GHA packaging build always uses the action
definition from `master` this change has to land before we can
successfully build the PR that does the actual renaming of the core
library and Debian package. Later we can remove the references to
`libkmnkbp0-0` again.
Part of #9733.
