Fix flaky parallel split query test: move ClearLog() before parallel tasks

[Copilot]

Can_query_with_nav_collection_in_projection_with_split_query_in_parallel_async intermittently failed with Expected: 400, Actual: 399 because ClearLog() was called inside each concurrent task. Task 2's ClearLog() could race and fire after Task 1 had already logged its first SQL statement, silently dropping it from the shared log.

• Move ClearLog() from inside each parallel task lambda to the outer test method, called once before tasks are launched
• Apply the same fix to the sync variant (Can_query_with_nav_collection_in_projection_with_split_query_in_parallel_sync)

// Before: ClearLog() inside each concurrent task — race condition
var task1 = QueryAsync(context1, ...);  // task starts, logs SQL...
var task2 = QueryAsync(context2, ...);  // ClearLog() wipes task1's already-logged entry

// After: cleared once, synchronously, before tasks start
ClearLog();
var task1 = QueryAsync(context1, ...);
var task2 = QueryAsync(context2, ...);

[Copilot]

Pull request overview

This PR addresses intermittent flakiness in the parallel split-query tests by removing a race condition in SQL log clearing: ClearLog() was previously invoked inside concurrently running task bodies, allowing one task to clear the shared TestSqlLoggerFactory log after the other task had already started logging.

Changes:

• Move ClearLog() to run once before starting parallel async tasks in Can_query_with_nav_collection_in_projection_with_split_query_in_parallel_async.
• Apply the same change to the sync parallel variant Can_query_with_nav_collection_in_projection_with_split_query_in_parallel_sync.