[MAINTENANCE] Move convert_to_json_serializable to top-level utils package

[Kilo59]

Move convert_to_json_serializable to the top-level utils package.
Nesting it within core.utils causes a lot of avoidable import cycles.

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[codecov]

Codecov Report

Attention: Patch coverage is 79.63801% with 45 lines in your changes are missing coverage. Please review.

Project coverage is 77.85%. Comparing base (1c0c2cb) to head (31eab4d).

Files	Patch %	Lines
great_expectations/util.py	76.50%	43 Missing ⚠️
great_expectations/core/util.py	50.00%	1 Missing ⚠️
...rule_based_profiler/helpers/runtime_environment.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #9933   +/-   ##
========================================
  Coverage    77.85%   77.85%           
========================================
  Files          454      454           
  Lines        39523    39517    -6     
========================================
- Hits         30770    30766    -4     
+ Misses        8753     8751    -2     

Flag	Coverage Δ
3.10	64.39% <76.01%> (-0.01%)	⬇️
3.10 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	?
3.10 aws_deps	?
3.10 big	?
3.10 databricks	?
3.10 filesystem	?
3.10 mssql	?
3.10 mysql	?
3.10 postgresql	?
3.10 snowflake	?
3.10 spark	?
3.10 trino	?
3.11	64.39% <76.01%> (+0.01%)	⬆️
3.11 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	53.62% <64.70%> (-0.01%)	⬇️
3.11 aws_deps	44.79% <59.72%> (-0.01%)	⬇️
3.11 big	53.84% <71.04%> (-0.01%)	⬇️
3.11 databricks	46.07% <61.08%> (-0.01%)	⬇️
3.11 filesystem	59.33% <70.58%> (-0.01%)	⬇️
3.11 mssql	49.06% <60.18%> (-0.01%)	⬇️
3.11 mysql	49.12% <63.34%> (-0.01%)	⬇️
3.11 postgresql	53.25% <65.61%> (-0.01%)	⬇️
3.11 snowflake	46.74% <61.08%> (-0.01%)	⬇️
3.11 spark	56.52% <68.32%> (-0.01%)	⬇️
3.11 trino	51.16% <65.15%> (-0.01%)	⬇️
3.8	64.42% <76.01%> (-0.01%)	⬇️
3.8 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	53.62% <64.70%> (-0.01%)	⬇️
3.8 aws_deps	44.81% <59.72%> (-0.01%)	⬇️
3.8 big	53.85% <71.04%> (-0.01%)	⬇️
3.8 databricks	46.09% <61.08%> (-0.01%)	⬇️
3.8 filesystem	59.34% <70.58%> (-0.01%)	⬇️
3.8 mssql	49.04% <60.18%> (-0.01%)	⬇️
3.8 mysql	49.10% <63.34%> (-0.01%)	⬇️
3.8 postgresql	53.24% <65.61%> (-0.01%)	⬇️
3.8 snowflake	46.76% <61.08%> (-0.01%)	⬇️
3.8 spark	56.48% <68.32%> (-0.01%)	⬇️
3.8 trino	51.15% <65.15%> (-0.01%)	⬇️
3.9	64.41% <76.01%> (-0.01%)	⬇️
3.9 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	?
3.9 aws_deps	?
3.9 big	?
3.9 databricks	?
3.9 filesystem	?
3.9 mssql	?
3.9 mysql	?
3.9 postgresql	?
3.9 spark	?
3.9 trino	?
cloud	0.00% <0.00%> (ø)
docs-basic	47.62% <56.56%> (+<0.01%)	⬆️
docs-creds-needed	48.74% <56.10%> (+<0.01%)	⬆️
docs-spark	47.47% <56.10%> (+<0.01%)	⬆️

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[billdirks]

This LGTM, except for the doc changes that @cdkini mentioned and the test you noted you should move.

Thanks for doing this!