Add support for bare Lambda function URLs

[MPLew-is]

Add request and response object models for invoking Lambda function URLs.

Motivation:

Instead of having to spin up (and pay for) API Gateway endpoints, Lambdas can spin up bare URLs for public access.
There are no existing request or response objects for these requests like there are for other event types.

Modifications:

• Created a FunctionURLRequest object matching the request payload format
• Created a FunctionURLResponse object matching the response payload format

These payloads are very similar (but not identical to) API Gateway V1 requests, so this is mostly just forked from that and tested until it works with simple requests.
Note that I have only tested completely public endpoints, and cannot speak for the accuracy of the Authorizer sub-type.

Result:

After this change, users will be able to write:

struct FunctionURLHandler: LambdaHandler {
	typealias Event  = FunctionURLRequest
	typealias Output = FunctionURLResponse

	func handle(_ event: Event, context: LambdaContext) async throws -> Output {
		...
	}
}

and then be able to simply invoke their Lambdas without API Gateway:

curl https://abcd1234.lambda-url.{region}.on.aws

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[tomerd]

@swift-server-bot test this please

[MPLew-is]

@tomerd I've added some test cases to this - any thoughts on getting this merged?

[tomerd]

@swift-server-bot test this please

[MPLew-is]

@tomerd it looks like the 5.5 and 5.6 builds are currently disabled, don't know if that will impact this being merged.