[EPIC] Use a single source for Presription structure

[VannTen]

Is your feature request related to a problem? Please describe.
#205 direct cause is that the producer (this repo) and the consummer (adviser) do not use a common structure for Prescription
Naturally, per Murphy's law, those definitions have diverged

Describe the solution you'd like
Use one single structure in both adviser and prescriptions-refresh-job, eventually in other thoth repos handling prescriptions.
In more details, I thought about the following plan:

• Use Python dataclass + pydantic validation instead of voluptous in adviser
• Create yaml from Prescriptions object (instead of the other way around) #209
• Implement/use generic serialization dataclass <-> YAML. (I'm pretty sure there is already something in Python ecosystem which does that)

Additional context

https://scribe.rip/parse-dont-validate-f559372cca45 (not directly relevant, but's that one of the motivation of thoth-station/adviser#2413 and seems relevant for this as well (5/10 min read)

[goern]

@mayaCostantini could you give us 15min and your opinion on this?

[VannTen]

/sig stack-guidance