Add load test for SQL Server subscription

[alexeyzimarev]

55K events produced and consumed in parallel

• Checks the last event's global position and ensures it's the number of produced messages minus one
• Ensures that the checkpoint is the same as the highest global position, so when all the events are consumed, the stored checkpoint matches the end of $all

[github-actions]

Test Results

  31 files    31 suites   18m 21s ⏱️
130 tests 129 ✔️ 0 💤 1 ❌
239 runs  238 ✔️ 0 💤 1 ❌

For more details on these failures, see this check.

Results for commit 5e52912.

♻️ This comment has been updated with latest results.