Restructure Project to support Dependency Injection

[acupofjose]

This pull represents a restructuring of the entire project to support Dependency Injection and Nullability (ref: supabase-community/supabase-csharp#34 and #16). Unfortunately this introduces some breaking API changes.

• Client is no longer a singleton class.
• Channel has a new constructor that uses ChannelOptions
• Channel.Parameters has been changed in favor of Channel.Options
• Channel and Push are now directly dependent on having Socket and SerializerSettings passed in as opposed to referencing the Singleton instance.
• All publicly facing classes (that offer functionality) now include an Interface.

In reality, not much should affect the developer as most of these classes/methods are only being referenced internally by the Client. The removal of the Singleton aspect may offer some design changes for those leveraging this library by itself (as opposed to using it only in supabase-csharp.)

// What was:
var client = Supabase.Realtime.Client.Initialize(options);
await client.ConnectAsync()

// Becomes:
var client = new Client(options);
await client.ConnectAsync()

[acupofjose]

@HunteRoi would you be up to take a look at this one? It's a bit bigger than the previous one.

[acupofjose]

Fixes #16

[veleek]

The Socket code that uses this asserts that the value is not null with the ! postfix operator. I don't see anything obvious that actually verifies this so it might be a good idea to add something or change this to be non-nullable.

[acupofjose]

It's set in the constructor!

realtime-csharp/Realtime/Client.cs

Lines 113 to 135 in cca23d2

	public Client(string realtimeUrl, ClientOptions? options = null)
	{
	this.realtimeUrl = realtimeUrl;
	if (options == null)
	options = new ClientOptions();
	if (options.Encode == null)
	options.Encode = (payload, callback) => callback(JsonConvert.SerializeObject(payload, SerializerSettings));
	if (options.Decode == null)
	{
	options.Decode = (payload, callback) =>
	{
	var response = new SocketResponse(SerializerSettings);
	JsonConvert.PopulateObject(payload, response, SerializerSettings);
	callback(response);
	};
	}
	Options = options;
	subscriptions = new Dictionary<string, Channel>();
	}