Optimize import: use models instead of emulating requests in loop

[ulcuber]

Description:

See #523

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed

[AltamashShaikh]

@ulcuber Thabks for the PR, but there is a reason we do not call the APIs directly as added in the PR and unfortunately we won't be able to merge this changes.