feat(gap): add ConnectionLatency in ConnectionParams

[acouvreur]

These settings are alternatives for platforms that do not support settings the MinInterval and MaxInterval directly.

I will follow up with a pull request adding support for Windows.
Edit: here is the follow up pull request: #423

The current enumeration is heavily inspired from https://developer.apple.com/documentation/corebluetooth/cbperipheralmanagerconnectionlatency

However, we could also use the enumeration from windows:

• ThroughputOptimized
• Balanced
• PowerOptimized

What do you think @deadprogram ?

[deadprogram]

I just wonder about this, in part because that would probably mean we need to decide what connection params would be associated with a latency level for platforms where it does not exist.

Maybe we should go the other direction, meaning determine what latency would best match a set of connection params?

[acouvreur]

We can create named ConnectionParams with a pre-defined set of values.

Then depending on the platform, they may use that how they want.

But what happens when using a non pre-defined for platforms that only support pre-defined set ?

---

Let me update the PR with the suggestions

[acouvreur]

Mmmmh. I wanted to do something like

var lowLatencyConnectionParams = ConnectionParams{
	MinInterval: NewDuration(7.5 * time.Millisecond),
	MaxInterval: NewDuration(15 * time.Millisecond),
	Timeout:     NewDuration(4 * time.Second),
}

var mediumLatencyConnectionParams = ConnectionParams{
	MinInterval: NewDuration(15 * time.Millisecond),
	MaxInterval: NewDuration(30 * time.Millisecond),
	Timeout:     NewDuration(4 * time.Second),
}

var highLatencyConnectionParams = ConnectionParams{
	MinInterval: NewDuration(30 * time.Millisecond),
	MaxInterval: NewDuration(60 * time.Millisecond),
	Timeout:     NewDuration(4 * time.Second),
}

func ConnectionParamsLowLatency() ConnectionParams {
	return lowLatencyConnectionParams
}

func ConnectionParamsMediumLatency() ConnectionParams {
	return mediumLatencyConnectionParams
}

func ConnectionParamsHighLatency() ConnectionParams {
	return highLatencyConnectionParams
}

But I don't like it.

I wanted to be able to do some equality comparison on windows for example but it won't work as I expect.