Make cel2sql generic using View abstraction

[RafaeLeal]

Changes

This PR makes the cel2sql package more generic, introducing a new View abstraction. This allows us to decouple what we expose for the Results' API filters and the database structure.

I believe it also makes changes in our database safer since we don't have to think of all kinds of filters that would use each column of the db table. The idea is to make the changes and support in the CEL filters more deliberate.

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Release Notes

Refactor cel2sql into a generic and extensible View abstraction

[alan-ghelardi]

/kind misc

[alan-ghelardi]

@RafaeLeal I left a few comments mostly about style and some parts of the code that I'd prefer to leave as before (tests, for example). You need to rebase the pr and write down release notes.

[tekton-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: adambkaplan

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[tekton-robot]

@RafaeLeal: PR needs rebase.

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