(synthetics): add static cron method to schedule class

[kaizencc]

cron expressions are now allowed on synthetic canaries. Similar to app-autoscaling and autoscaling and other modules, the synthetic Schedule class should support a static cron method that takes in cronOptions.

I think we can (and should) talk about moving Schedule to core. I tried that in #9250 and perhaps we can revive that conversation.

Use Case

Syntactic sugar and to offer the same user experience across modules.

Proposed Solution

Here's how its done in application autoscaling:

aws-cdk/packages/@aws-cdk/aws-applicationautoscaling/lib/schedule.ts

Lines 47 to 62 in 492d33b

	public static cron(options: CronOptions): Schedule {
	if (options.weekDay !== undefined && options.day !== undefined) {
	throw new Error('Cannot supply both \'day\' and \'weekDay\', use at most one');
	}
	const minute = fallback(options.minute, '*');
	const hour = fallback(options.hour, '*');
	const month = fallback(options.month, '*');
	const year = fallback(options.year, '*');
	// Weekday defaults to '?' if not supplied. If it is supplied, day must become '?'
	const day = fallback(options.day, options.weekDay !== undefined ? '?' : '*');
	const weekDay = fallback(options.weekDay, '?');
	return new LiteralSchedule(`cron(${minute} ${hour} ${day} ${month} ${weekDay} ${year})`);
	}

Other

The current work around is to use Schedule.expression('cron(* * * * *)').
Related: #16392.

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

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This is a 🚀 Feature Request

[github-actions]

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