Added ToHashSetAsync<T> Extension methods on IQueryable<T>

[wertzui]

Added ToHashSetAsync Extension methods on IQueryable

• Added ToHashSetAsync(this IQueryable source, CancellationToken cancellationToken = default)
• Added ToHashSetAsync(this IQueryable source, IEqualityComparer? comparer, CancellationToken cancellationToken = default)

Fixes #30033

[wertzui]

@dotnet-policy-service agree

[ajcvickers]

Thanks for the contribution!

[wertzui]

Thanks for approving it, I wanted to have ToHashSetAsync for quite some time.