fix: utf-16 json encoder support

[eyalezer]

SUMMARY

Following the pessimistic json encoder fix and an issue reported in https://github.com/apache/superset/issues/28372 which fails to decode UTF-16 bytes in SQL Lab. Added UTF-16 encoding support for json serialization.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 77.77778% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 83.43%. Comparing base (76d897e) to head (a676d10). Report is 112 commits behind head on master.

Files	Patch %	Lines
superset/sqllab/execution_context_convertor.py	60.00%	2 Missing :warning:

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #28486       +/-   ##
===========================================
+ Coverage   60.48%   83.43%   +22.94%     
===========================================
  Files        1931      521     -1410     
  Lines       76236    37429    -38807     
  Branches     8568        0     -8568     
===========================================
- Hits        46114    31228    -14886     
+ Misses      28017     6201    -21816     
+ Partials     2105        0     -2105     

Flag	Coverage Δ
hive	49.07% <33.33%> (-0.09%)	:arrow_down:
javascript	?
mysql	77.14% <77.77%> (?)
postgres	77.25% <77.77%> (?)
presto	53.63% <33.33%> (-0.17%)	:arrow_down:
python	83.43% <77.77%> (+19.94%)	:arrow_up:
sqlite	76.70% <77.77%> (?)
unit	58.80% <44.44%> (+1.18%)	:arrow_up:

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[mistercrunch]

Looks like tests are failing ...

[eyalezer]

indeed missed one integration test and also i see now some format issues, will fix both

[eyalezer]

@mistercrunch - Fixed and tested locally both formats and integration tests

[eyalezer]

@mistercrunch Discovered additional instances throughout the system that are still uncovered... i'll create a new pr for those