Add FIFO (First-In-First-Out) Cache Policy Implementation

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What is FIFO?

• FIFO is a cache policy where the first item added to the cache is the first one to be removed when space is needed

Here are the is what you will do:

1. Create a new struct FIFOCachePolicy that implements the CachePolicy interface
2. Track order of insertion using a slice or linked list to maintain FIFO order. You can use external libraries to for datastrucutres if you wish to use some.
3. Implement both required methods:
   • Eject(m *Memoria, requiredSpace uint64) error
   • Insert(m *Memoria, key string, val []byte) error

Example :

type FIFOCachePolicy struct {
    order []string  
   queue *queue
}