Refactor namespaces for DEX job behaviors

Updated namespaces for `CheckQueryExecutionBehavior`,
`MainQueryExecutionBehavior`, and `ReCRequestExecutionBehavior`
from `ECMJobRunner.Application.Behaviors` to
`ECMJobRunner.Application.DEXJob.Commands.Behaviors` to better
align with the `DEXJob.Commands` context.

Updated `DependencyInjection.cs` and test files to reference the
new namespace. Added `using Microsoft.Extensions.Options;` to
support the Options pattern in the updated files.

ECMJobRunner.Application/DependencyInjection.cs

@@ -1,4 +1,4 @@
-using ECMJobRunner.Application.Behaviors;
+using ECMJobRunner.Application.DEXJob.Commands.Behaviors;
 using MediatR;
 using Microsoft.Extensions.DependencyInjection;
 using ReC.Client;