[DOCS] Initial revision and reorg of "Create a Data Context" content for revised GX 1.0 ToC

[Rachel-Reverie]

Description

• Adds "Create a Data Context" topic to the "Set up a GX environment" category.
• Updates example scripts to utilize the mode parameter when instantiating a specific type of Data context.

Definition of done

• PR title is prefixed with one of: [BUGFIX], [FEATURE], [DOCS], [MAINTENANCE], [CONTRIB]
• Code is linted - run invoke lint (uses ruff format + ruff check)
• Appropriate tests and docs have been updated

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.08%. Comparing base (f96a49b) to head (a3b1f9e).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #9938   +/-   ##
========================================
  Coverage    79.08%   79.08%           
========================================
  Files          454      454           
  Lines        38488    38488           
========================================
  Hits         30439    30439           
  Misses        8049     8049           

Flag	Coverage Δ
3.10	65.31% <ø> (ø)
3.11	65.31% <ø> (ø)
3.11 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	54.07% <ø> (ø)
3.11 aws_deps	45.23% <ø> (ø)
3.11 big	54.20% <ø> (ø)
3.11 databricks	46.36% <ø> (ø)
3.11 filesystem	60.02% <ø> (ø)
3.11 mssql	49.43% <ø> (ø)
3.11 mysql	49.49% <ø> (ø)
3.11 postgresql	53.73% <ø> (ø)
3.11 snowflake	47.04% <ø> (ø)
3.11 spark	57.03% <ø> (ø)
3.11 trino	51.59% <ø> (ø)
3.8	65.34% <ø> (ø)
3.8 athena or clickhouse or openpyxl or pyarrow or project or sqlite or aws_creds	54.08% <ø> (ø)
3.8 aws_deps	45.25% <ø> (ø)
3.8 big	54.21% <ø> (ø)
3.8 databricks	46.37% <ø> (ø)
3.8 filesystem	60.03% <ø> (ø)
3.8 mssql	49.41% <ø> (ø)
3.8 mysql	49.47% <ø> (ø)
3.8 postgresql	53.71% <ø> (ø)
3.8 snowflake	47.06% <ø> (ø)
3.8 spark	56.99% <ø> (ø)
3.8 trino	51.57% <ø> (ø)
3.9	65.33% <ø> (ø)
cloud	0.00% <ø> (ø)
docs-basic	48.19% <ø> (ø)
docs-creds-needed	49.35% <ø> (ø)
docs-spark	48.13% <ø> (ø)

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