[Incremental Aggregation] Optimise table lookups in querying & synchronise aggregation process function

[niveathika]

Purpose

$subject, to reduce the memory usage when querying aggregation tables.(Fixes #491)
Synchronize aggregation process method

Goals

Optimize querying aggregation tables.

Approach

Pass aggregation on condition to the tables.

Documentation

N/A

Automation tests

• Unit tests - 79%
• Integration tests - N/A

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? yes
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes

[codecov-io]

Codecov Report

Merging #1310 into master will decrease coverage by 0.18%.
The diff coverage is 32.94%.

@@             Coverage Diff              @@
##             master    #1310      +/-   ##
============================================
- Coverage     63.11%   62.92%   -0.19%     
  Complexity       37       37              
============================================
  Files           621      623       +2     
  Lines         25384    25554     +170     
  Branches       3974     4005      +31     
============================================
+ Hits          16020    16081      +61     
- Misses         8088     8193     +105     
- Partials       1276     1280       +4

Impacted Files	Coverage Δ	Complexity Δ
...o/siddhi/core/aggregation/IncrementalExecutor.java	81.34% <ø> (ø)	0 <0> (ø)	⬇️
.../siddhi/core/aggregation/RecreateInMemoryData.java	52.38% <100%> (+0.57%)	0 <0> (ø)	⬇️
...io/siddhi/core/aggregation/AggregationRuntime.java	92.66% <100%> (+0.75%)	0 <0> (ø)	⬇️
...core/aggregation/AggregationExpressionBuilder.java	21.66% <21.66%> (ø)	0 <0> (?)
...core/aggregation/AggregationExpressionVisitor.java	27.36% <27.36%> (ø)	0 <0> (?)
...dhi/core/util/parser/helper/QueryParserHelper.java	96.1% <0%> (-0.65%)	0% <0%> (ø)
...i/core/util/parser/CollectionExpressionParser.java	38.28% <0%> (+0.9%)	0% <0%> (ø)	⬇️
...ut/stream/state/AbsentStreamPreStateProcessor.java	86.61% <0%> (+1.4%)	0% <0%> (ø)	⬇️
... and 2 more

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