Update Index and IndexInterface docstrings with RST formatting and code examples

[jhamon]

Summary

This PR updates all docstrings for methods in the Index class and the underlying IndexInterface class to use proper RST syntax with comprehensive code-block examples.

Changes

• Updated all Index class method docstrings with:

  • Proper RST formatting using Args/Returns/Examples sections
  • Comprehensive code-block examples showing different usage patterns
  • Proper whitespace formatting (empty lines after code blocks for Sphinx rendering)

• Updated IndexInterface class docstrings to:

  • Match the Index class style and formatting
  • Use consistent RST formatting throughout
  • Include code-block examples for all methods
  • Remove old :param: and :type: syntax in favor of Args sections

Methods Updated

All methods in both classes now have complete, up-to-date docstrings:

• upsert, upsert_from_dataframe, upsert_records
• search, search_records
• delete, fetch, fetch_by_metadata
• query, query_namespaces
• update, describe_index_stats
• list, list_paginated
• create_namespace, describe_namespace, delete_namespace
• list_namespaces, list_namespaces_paginated
• Import-related methods (start_import, list_imports, etc.)

Impact

• Improved documentation quality and consistency
• Better IDE support with comprehensive examples
• Proper Sphinx rendering with correct whitespace formatting
• All docstrings now follow RST best practices