Fixing SORTABLE, INDEXEMPTY and INDEXMISSING order when using RediSearch fields

[petyaslavova]

Pull Request check-list

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Description of change

Fixes #3809

[Copilot]

Pull Request Overview

This PR fixes the ordering of RediSearch field attributes in index creation commands. The SORTABLE attribute must appear after INDEXEMPTY and INDEXMISSING to comply with RediSearch's expected command syntax.

Key Changes:

• Reordered field attribute appending logic to place SORTABLE after INDEXEMPTY and INDEXMISSING
• Added test coverage for the fixed behavior in both sync and async test suites

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
redis/commands/search/field.py	Moved SORTABLE attribute to be appended after INDEXEMPTY and INDEXMISSING in the Field constructor
tests/test_search.py	Added test case verifying index creation with SORTABLE combined with INDEXEMPTY and INDEXMISSING
tests/test_asyncio/test_search.py	Added async version of the test case for index creation with combined attributes

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