Abstraction for project/chroot/package/build/webhook/(user) configuration

[FrostyX]

We have inconsistencies that it is possible to configure some features per project but not per chroot or the other way around. We should add some abstraction to define it once, and have it everywhere for free.

[praiskup]

We should start with the --timeout option.

[penguinpee]

I just ran up against this looking at the max number of builds setting for packages. This one would definitely benefit from having a global per repo setting, rather than per package. The per package setting could then be used as an overwrite of the repo's default.

[xambroz]

I am missing per-build option "--with something" ... currently possible on chroot level, but for rebuilding packages with circular dependencies it is bit cumbersome to change it back and forth. More info #3272