fix(linter): add help text to eslint rule diagnostics

[anthonyamaro15]

PR covers:

Closes #19121 (partially)

Add .with_help() to 5 ESLint rule diagnostics:

• no-new: "Assign the result of 'new' to a variable or compare it to a reference."
• no-multi-str: "Multiline strings are not allowed. Use template literals or string concatenation
  instead."
• no-label-var: "Rename either the variable or the label to avoid confusion."
• no-nested-ternary: "Refactor nested ternary expressions into if-else statements for better
  readability."
• no-func-assign: "Do not re-assign a function declared as a FunctionDeclaration."

5 rule files changed + 5 corresponding snapshot updates.

[Copilot]

Pull request overview

This PR adds helpful guidance text to 5 ESLint rule diagnostics, making error messages more actionable for developers. This is part of a larger effort (issue #19121) to ensure all linter diagnostics provide clear instructions on how to fix issues.

Changes:

• Added .with_help() to 5 ESLint rules with actionable guidance on how to fix the detected issues
• Updated corresponding snapshot files to reflect the new help text in diagnostic output

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/oxc_linter/src/rules/eslint/no_new.rs	Added help text instructing to assign the result of 'new' to a variable or compare it to a reference
crates/oxc_linter/src/rules/eslint/no_multi_str.rs	Added help text suggesting template literals or string concatenation as alternatives
crates/oxc_linter/src/rules/eslint/no_label_var.rs	Added help text advising to rename either the variable or label to avoid confusion
crates/oxc_linter/src/rules/eslint/no_nested_ternary.rs	Added help text recommending refactoring to if-else statements for better readability
crates/oxc_linter/src/rules/eslint/no_func_assign.rs	Added help text warning against re-assigning function declarations
crates/oxc_linter/src/snapshots/eslint_no_new.snap	Updated snapshot to include new help text for no_new rule
crates/oxc_linter/src/snapshots/eslint_no_multi_str.snap	Updated snapshot to include new help text for no_multi_str rule
crates/oxc_linter/src/snapshots/eslint_no_label_var.snap	Updated snapshot to include new help text for no_label_var rule
crates/oxc_linter/src/snapshots/eslint_no_nested_ternary.snap	Updated snapshot to include new help text for no_nested_ternary rule
crates/oxc_linter/src/snapshots/eslint_no_func_assign.snap	Updated snapshot to include new help text for no_func_assign rule

[codspeed-hq]

Merging this PR will not alter performance

✅ 47 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing anthonyamaro15:fix/eslint-diagnostics-add-help-text-2 (1c5bbfb) with main (89b58d0)}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[camc314]

Thank yoU!