hll memory estimate in MB instead of Bytes

[jshencode]

this drastically under estimate memory usage for hll query and cause out of memory situation during massive hll query hits, such as weekly hll contracts

[codecov[bot]]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (56108d0) 71.88% compared to head (6b14771) 71.89%. Report is 47 commits behind head on master.

Files	Patch %	Lines
query/aql_processor.go	0.00%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff            @@
##           master     #312    +/-   ##
========================================
  Coverage   71.88%   71.89%            
========================================
  Files         166      166            
  Lines       23252    23367   +115     
========================================
+ Hits        16714    16799    +85     
- Misses       5246     5275    +29     
- Partials     1292     1293     +1     

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