Added print functionality to iters to allow simpler debugging

[redixhumayun]

What This PR Does

• Adds print functionality to all iterators
• Ensures proper formatting for each iterator

Sample output for a two merge iterator shown below

xxxxxxxxxx    TWO_MERGE_ITERATOR     xxxxxxxxxx
----------        ITERATOR A         ----------
----------      Merge Iterator       ----------

Current Iterator (Index 1):
----------     Memtable Iterator     ----------
Key       : "00"
Value     : "2333"
----------   End Memtable Iterator   ----------

Iterators in Heap: 1
Iterator Index 0: Valid
----------     Memtable Iterator     ----------
Key       : "1"
Value     : ""
----------   End Memtable Iterator   ----------
----------    End Merge Iterator     ----------
----------      END ITERATOR A       ----------

----------        ITERATOR B         ----------
----------      Merge Iterator       ----------

Current Iterator (Index 1):
----------       SST_ITERATOR        ----------
Current Block Index: 0
----------      Block Iterator       ----------
First Key           : "0"
Current Key         : "0"
Current Value       : "2333333"
Key Index           : 0
==========   Block    ==========
Index     : 0
Key       : 0
Value     : 2333333
--------------------
Index     : 1
Key       : 00
Value     : 2333333
--------------------
Index     : 2
Key       : 4
Value     : 23
--------------------
Offsets: [0, 14, 28]
========== End Block  ==========
----------    Block Iterator End     ----------
----------     SST_ITERATOR_END      ----------

Iterators in Heap: 1
Iterator Index 0: Valid
----------       SST_ITERATOR        ----------
Current Block Index: 0
----------      Block Iterator       ----------
First Key           : "4"
Current Key         : "4"
Current Value       : ""
Key Index           : 0
==========   Block    ==========
Index     : 0
Key       : 4
Value     : 
--------------------
Offsets: [0]
========== End Block  ==========
----------    Block Iterator End     ----------
----------     SST_ITERATOR_END      ----------
----------    End Merge Iterator     ----------
----------      END ITERATOR B       ----------
xxxxxxxxxx  END TWO_MERGE_ITERATOR   xxxxxxxxxx

Questions

• One point to note is that the decoding scheme used for a block is the compressed key format implemented on week 1 day 7. Should that be the decoding scheme while printing?
• Should this be left as an exercise for the student since they are expected to implement an encoding decoding scheme anyway?