Integrate gitlab-ci/unify-image-and-sdk-package-jobs and 3 more

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@5762a54c

Yocto build: unify image and SDK package jobs

Image and SDK package jobs call the same package script just with
different arguments. Instead of having two job classes `package_release`
and `package_sdk` for these two tasks, merge them into the base class
`package` and make the differences configurable via a variable
`PACKAGE_TYPE`.

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@8e72eac2

Yocto build: add variable for manual builds

Instead of hard-coding the rules for manual builds in each actual job,
conditionally add this to the `buildbase` class and add a variable
`MANUAL_BUILD` to the according jobs.

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@e6d71996

Yocto build: unify image and SDK build jobs

Image and SDK builds share a lot of similar code. Instead of having two
job classes `build_yocto_image` and `build_yocto_sdk` for these two
tasks, merge them into the base class `build_yocto` and make the
differences configurable via a variable.

The `dump_install_command` part of the script, which was not executed
for SDK builds, is always present now, but it's only executed if the
`INSTALLSCRIPT` variable is set, which is not the case for SDK builds.

The `collect_srcrevs` part of the script is executed in all cases. It
was not part of the SDK build before, but it's not less relevant there.

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@f892500f

Yocto build: make main artifacts path configurable

Instead of specifying all possible artifacts paths and abusing the fact
that GitLab ignores non-existing paths during artifact upload, implement
a cleaner solution with a configurable path.