refactor: sql_json view endpoint: separate flask response creation concern

[ofekisr]

SUMMARY

The sql_json view code in superset core view without any "clean code" standard and it does not adopt any software development principle.

This is the eleventh PR in the sequence of future PRs (previous PR) try to solve it by refactoring the code.

The PR focus on separating the creating the flask response concern from multiple methods to one place.
This is the first PR who build the basis so the code will be able to be separated into layers

there are no logic changes so it implies on the current tests.

[codecov]

Codecov Report

Merging #16676 (f40ac66) into master (1429d9d) will increase coverage by 0.07%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##           master   #16676      +/-   ##
==========================================
+ Coverage   76.84%   76.91%   +0.07%     
==========================================
  Files        1005     1005              
  Lines       54019    54017       -2     
  Branches     7337     7337              
==========================================
+ Hits        41509    41547      +38     
+ Misses      12270    12230      -40     
  Partials      240      240              

Flag	Coverage Δ
hive	81.25% <85.71%> (+<0.01%)	⬆️
mysql	81.59% <85.71%> (-0.04%)	⬇️
postgres	81.69% <85.71%> (+<0.01%)	⬆️
presto	81.53% <85.71%> (?)
python	82.19% <85.71%> (+0.14%)	⬆️
sqlite	81.30% <85.71%> (+0.04%)	⬆️

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Impacted Files	Coverage Δ
superset/views/core.py	76.24% <85.71%> (+0.03%)	⬆️
superset/models/core.py	89.40% <0.00%> (+0.25%)	⬆️
superset/connectors/sqla/models.py	89.70% <0.00%> (+1.42%)	⬆️
superset/db_engine_specs/presto.py	89.95% <0.00%> (+5.43%)	⬆️

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[amitmiran137]

LGTM