using await on types implementing IAsyncDisposable

[AmirShitrit]

Description

Using await using on types implementing IAsyncDisposable.
Also, awaiting on ExecuteNonQueryAsync where it's used, in order to get a clearer callstack when exceptions are thrown.
In addition, returning index + 1 in PersistEventAsync instead of index++ which also needlessly modifies index.

Purpose

This pull request is a:

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Simple performance and debuggability improvements

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• No new tests are necessary