Closes coder/internal#674

Description:

• Throttle notifications to template admins: send no more than one notification per 7 days.
• Throttle notifications to template version author: send no more than one notification per 1 day.

Note:
It's done per template:

CREATE TABLE template_prebuild_notification_cooldowns (
	template_id UUID NOT NULL,
	notification_type TEXT NOT NULL,
	last_notification_sent TIMESTAMPTZ NOT NULL,
	PRIMARY KEY (template_id, notification_type)
);

We can have multiple broken templates - in this case Template Admins will get one notification per template per 7 days.
I think it shouldn't be more than few notifications per week.

If it's still too noisy - we can consider making cooldowns global instead of template-specific. It should be enough to remove template_id field.