[uss_qualifier] check constraint reference synchronization across multiple DSS instances

[Shastick]

Adds a scenario the checks that Constraint References are properly synchronized across a set of DSS instances.

This is a relatively big PR. The new validator and scenario are an almost 1-1 equivalent of what is done for the operational intents.

Part of the effort tracked by #434

[BenjaminPelletier]

I haven't been able to find a block of time big enough to fully cache this entire PR -- I think we should split it into smaller pieces unless @mickmis or @barroco are able to review instead

[Shastick]

I put that on my list of things to do for Friday. Splitting this according to each step of the scenario should not be problematic.

[Shastick]

@BenjaminPelletier the first slice has been pushed to #704

edit: Note, a series of PRs is now ready on:

• [uss_qualifier] initial constraint reference sync scenario - creation - 1/n #704
• [uss_qualifier] constraint references: check created references are synced - 2/n #705
• [uss_qualifier] constraint reference sync: check created references can be searched - 3/n #706
• [uss_qualifier] constraint reference sync: cover mutations 4/n #707
• [uss_qualifier] constraint reference sync: cover deletion 5/5 #708

All except the first one are left as draft, but they are ready for review: if anyone would want to look at them, you may see the relevant changes by only showing the changes of the last commit.