fix: Fix not being able to see some templates (#5705)

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Robin noticed that when he had a `hubspot/users` sync previously
deployed (and disabled now), the new `hubspot/sync-users` template
wasn't even available to turn on. This was the case for a few other
syncs too.

The reason for that is we are filtering templates that sync models with
the same name as any other previously deployed sync. Since syncs can't
influence models from other syncs, this doesn't seem to make sense.
<!-- Issue ticket number and link (if applicable) -->

<!-- Testing instructions (skip if just adding/editing providers) -->


<!-- Summary by @propel-code-bot -->

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This PR updates flow template deduplication so templates are no longer
filtered out solely due to sharing model names with previously deployed
syncs, and adds an integration test to ensure renamed templates remain
visible when legacy syncs exist.

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*This summary was automatically generated by @propel-code-bot*