Agent should always create the "error" intrinsics attribute

[vuqtran88]

Description
In the event of error occurs in a transaction, the agent create the "error" intrinsics attribute and set its value to "true" in it for transaction event. However, It doesn't create this attribute for "normal" transactions.

Expected Behavior
Agent creates the "error" intrinsics attribute for transaction events with/without errors and set the value appropriately.

Your Environment
[TIP]: # ( Include as many relevant details about your environment as possible including the running version of the agent and any relevant configurations, such as the .NET framework or core version of your application. )

Additional context
Refs:

newrelic-dotnet-agent/src/Agent/NewRelic/Agent/Core/Transformers/TransactionTransformer/TransactionAttributeMaker.cs

Line 99 in 9d6ae8f

_attribDefs.IsError.TrySetValue(attribValues, true);

https://pages.datanerd.us/engineering-management/architecture-notes/notes/123/#error-tracking

After discussing with other agent engineers, sees the below:

• Python and Ruby agents also don't send error attribute with false value while Java agent does. I haven't gotten the responses from the rest of other team. The reasons are:

     1. There are other New Relic components that we don't own that might rely on just the present of this attribute. This might no longer be true as I check with distributed tracing team.
     
     2. We're not supposed to send values who's value is the same as the implicit/default value even though this is definitely not obvious to customers.
  

• Even though I created a bug there, but it will require some coordination with other agents as this will be a breaking change for some customers (null value error attribute will no longer be there if we decided to fix.). However, the spec is clear when the spec is clear on what it should be. It won't be an immediate breaking change since customers would have to update to get the fix. We need to do good communication with the customers if we decided to make this change.