Provide an endpoint to list critpath components

[mattiaverga]

Let's have a way to provide information about what Bodhi consider to be in critical path.
WIP: I need to write some tests

@AdamWill If a user searches for collection=rawhide or collection=f40 we need the code to redirect to master.json. Do we have convenient symlinks set up? Otherwise I can do that in read_critpath_json

[AdamWill]

It's not master.json, it's rawhide.json. When you trace it all out, collection in this context is the git branch name. No, the script does not currently generate symlinks...I kinda don't mind whether we have the script create symlinks or just make read_critpath_json translate...

https://pagure.io/releng/blob/main/f/scripts/critpath.py#_345