fix(logs): correct CloudWatch query sort direction

[SergioChan]

Summary

• Fix CloudWatch Logs query sort direction mapping so sort ... desc uses descending order and sort ... asc uses ascending order.
• Update existing logs query tests to match the documented/default behavior (desc by default, asc when requested).

Testing

• python -m py_compile moto/logs/logs_query/query_parser.py moto/logs/logs_query/__init__.py tests/test_logs/test_logs_query/test_query.py
• Note: full pytest execution was not run in this environment because test dependencies are unavailable.

Related

Fixes #9818

[bblommers]

There's already an open PR to fix this: #9819