[Validators] - Review and improve warn/error message in order to provide how to sort them out

[camilamacedo86]

Description

See an example of the warns/issues raised by the validators: redhat-openshift-ecosystem/community-operators-pipeline#252 (comment)

The goal of this task is to ensure that all messages contain what is wrong/or could be improved with the suggested action to sort out the need.

Note that we can:

• Provide the steps to solve the problem
• Describe in the message why the suggestion is important and what happens when an author does not follow up on that
• Add links for the public docs (SDK, see: https://sdk.operatorframework.io/docs/best-practices/ )

[camilamacedo86]

@ryantking @mvalarh @J0zi @dmesser

I tracked here the need based on the feedback, I will try when in my spare time looking on that as well.
However, it can also tackle by anyone by doing PRs against this repo to improve the messages. Note that a PR doe not need to improve all messages and can be very punctual as well.