build-generic: refactor and document job templates
Split the existing .workspace and .build jobs into the following:
- .workspace - handling git-repo and single-repository CI override
- .bitbake-workspace - handling bitbake customizations, including recipe CI
- .build-{linux,zephyr,freertos} - build a tailored set of recipes
- .build-recipe - build a single recipe
- .build-image - build a single recipe and collect the resulting image
- .build - (deprecated) - alias for .build-recipe
This should keep compatibility with downstream CI (meta-ohos and others) but allow the docs repository to reuse the .workspace job entirely.
In addition, document all the jobs with reStructured Text, moving some of the text from the implementation (yaml) files, into new documentation chapters. Existing documentation is slightly re-structured to take the new implementation details into account.
In last addition, the .workspace job is no longer strict about presence of a directory called "sources/". This prevented re-using the job for gitee builds.
Signed-off-by: Zygmunt Krynicki zygmunt.krynicki@huawei.com