Organize dependency build processes

[dervoeti]

Implementation of https://github.com/stackabletech/decisions/issues/44

See sub-issues for the list of goals.

Non-Goal:

• Publishing artifacts (e.g., JARs in a Maven repository) is out of scope for this issue. This will be addressed when implementing stackabletech/issues#674.

[dervoeti]

• Source code is pulled from Github instead of Nexus in our Docker builds
• bake supports subdirectories which allowed us to organize the Dockerfiles into modules in separate nested directories
• Our container images contain .tar.gz archives with the exact source code that was used to build the product
• Products which we build from source report custom versions now (e.g. 3.9.3-stackable25.7.0 instead of 3.9.3)
• We have a process based on patchable to check out source code and apply patches to it, which in combination with the bake subdirectory support also allows us to create custom patches for dependencies (documentation present in Nuclino)
• Vulnerabilities decreased by a lot because products can use our custom patched libraries of e.g. Hadoop instead of pulling the unpatched versions from Maven Central