Add more options to create a jetstream.GetMsgOpt

[zerolfx]

Proposed change

The proposal is to have a similar version with the following code but set req.LastFor = subject.

nats.go/jetstream/jetstream_options.go

Lines 94 to 102 in 48391f1

	// WithGetMsgSubject sets the stream subject from which the message should be
	// retrieved. Server will return a first message with a seq >= to the input seq
	// that has the specified subject.
	func WithGetMsgSubject(subject string) GetMsgOpt {
	return func(req *apiMsgGetRequest) error {
	req.NextFor = subject
	return nil
	}
	}

Use case

I want to get the last message with a specific subject whose seq is <= a given one.

Contribution

No response