Add a possibility of reading gsfa from the oldest transaction to the newest

[linuskendall]

For some use cases we might want to be able to read gsfa not from newest to oldest but from oldest to newest.

This would require a method that finds the offset of the oldest transaction by reading all the transactions offsets until it finds one without the 'next' bytes available. Then start returning the transactions in the opposite order.

yellowstone-faithful/gsfa/linkedlog/linked-log.go

Line 133 in 797ed6c

func (s *LinkedLog) ReadWithSize(offset uint64, size uint64) ([]OffsetAndSizeAndBlocktime, indexes.OffsetAndSize, error) {