DRAFT: Add Painless debugging section

[kilfoyle]

~~ DRAFT ONLY ~~

Nothing to see here. 👀
Not yet ready for review. :-)

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Summary

This replaces the Painless section that was proposed for the Troubleshooting section of the docs, to instead be a "Debugging Painless scripts" section within the Explore & Analyze Painless docs.

To my mind, this has two advantages:

• These Painless pages aren't true "troubleshooting" docs ,and I think would not fit well into the Symptoms / Diagnosis / Resolution format that is now standard for that section. Debugging, here, is something that people need to be mindful of as they're composing their scripts, rather than a spontaneous error that needs diagnosis and recovery.
• Embedding this content into the existing Explore and Analyze section means that we have our Painless info in two locations (narrative + reference), rather than split across three separate parts of the docs. Much better as a user experience, IMHO.

Other changes still to come, based on @yetanothertw's comments in the roiginal PR.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

Vale Linting Results

Summary: 4 suggestions found

💡 Suggestions (4)

File	Line	Rule	Message
explore-analyze/scripting/painless-regex-pattern-matching-failures.md	14	Elastic.WordChoice	Consider using 'deactivated, deselected, hidden, turned off, unavailable' instead of 'disabled', unless the term is in the UI.
explore-analyze/scripting/painless-regex-pattern-matching-failures.md	14	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
explore-analyze/scripting/painless-type-casting-issues.md	109	Elastic.Wordiness	Consider using 'because' instead of 'since'.
explore-analyze/scripting/painless-type-casting-issues.md	109	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.

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[github-actions]

🔍 Preview links for changed docs

• explore-analyze/scripting/painless-array-list-manipulation-errors.md
• explore-analyze/scripting/painless-date-math-errors.md
• explore-analyze/scripting/painless-field-not-found.md
• explore-analyze/scripting/painless-ingest-pipeline-failures.md
• explore-analyze/scripting/painless-null-pointer-exceptions.md
• explore-analyze/scripting/painless-regex-pattern-matching-failures.md
• explore-analyze/scripting/painless-runtime-field-exceptions.md
• explore-analyze/scripting/painless-sandbox-limitations.md
• explore-analyze/scripting/painless-script-score-calculation-errors.md
• explore-analyze/scripting/painless-scripting.md

More links …

• explore-analyze/scripting/painless-subfield-access.md
• explore-analyze/scripting/painless-type-casting-issues.md