Feat: Improve cv_validate documentation

[pmprado]

Enhancement summary

The documentation of this module seems targeted to devs that already know why and what they need this module for.
An use case and a brief working example would be really helpful when evaluating if this is the best API call to use.

Which component of AVD is impacted

cv_device_v3

Use case example

Customer wants to be able to see the changes that would result, right from the AVD run, without modifying the configlets on CV.

Describe the solution you'd like

Using my use case as a guide, show a configlet with the current config, a new config generated by AVD, the playbook run and the result.

Describe alternatives you've considered

Manually pulling all the configlet contents and running a local diff

Additional context

No response

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