Handle ignoring of duplicates the same when not using INSERT SELECT

[sgiehl]

Description:

If INSERT INTO ... SELECT can not be used due to unsupported transaction level changes, Matomo falls back to performing a SELECT query followed by an INSERT query.

Both behaviors currently differ by the fact, that INSERT INTO ... SELECT ignores duplicates on purpose, while the pure INSERT statement doesn't.

This PR adjusts the pure INSERT statement, so it also ignores duplicates.

refs #18937

(Ref DEV-3515)

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