Change has_many :organizations on Group to has_many :crm_organizations

What does this MR do and why?

This is similar to the change we did in !118584 (merged).

Since we are going to be using the term organization heavily when building out cells, we do not want to clash with the existing has_many :organizations association on Group, which is under customer_relations/, so we are renaming the existing association and all it's usages to has_many: crm_organizations.

No changelog added as this is only a refactor of internal details.

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Related to #408632 (closed)