Add throttleKbps, delayMs with presets to StaticResponse objects

[flotwig]

Current behavior:

Users have to invoke .delay() or .throttle() to delay/throttle the response, and they have to use plain numbers (ms and kbps, respectively) to set the throttle:

cypress/packages/driver/test/cypress/integration/commands/net_stubbing_spec.ts

Lines 766 to 774 in 2443eb4

	cy.route2('/timeout', (req) => {
	req.reply((res) => {
	this.start = Date.now()
	res.throttle(kbps).delay(delayMs).send({
	statusCode: 200,
	body: payload,
	})
	})

Desired behavior:

Users should be able to statically define throttleKbps or delayMs, and should be able to use string presets. So the above code could be written as this:

cy.route2('/timeout', {
	statusCode: 200,
	body: payload,
	delayMs,
	throttle: '3g', 
})

For the list of throttle presets, we can probably use the same list that Chromium/WebKit use: https://source.chromium.org/chromium/chromium/src/+/master:chrome/test/chromedriver/chrome/network_list.cc;l=12;drc=23bc3b1c92fd920d4d359ba46d73054ff0f47d2c?originalUrl=https:%2F%2Fcs.chromium.org%2F

Depends on #687

[cypress-bot]

The code for this is done in cypress-io/cypress#8109, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 5.2.0.

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