Ensure that the event listener gets all the events

[sugmanue]

Description of changes:

Currently not all events are passed to the listener given the way this is implemented, e.g., if some part of logic add a set of events directly to the list using addAll. In particularLoaderShapeMap adds all the events to the events list for each ShapeModifier here which are then not shown in the output. Validation for the following model

$version: "2.0"

namespace com.amazon.example
structure Mixin1 {
    a: String
}

structure Valid with [Mixin1] {
    a: Integer
}

Will currently output

$ smithy validate ~/tmp/test-model5.smithy
FAILURE: Validated 211 shapes (ERROR: 1)

After this change it will output

ERROR: com.amazon.example#Valid$a (Model)
     @ /Users/sugmanue/tmp/test-model5.smithy
     |
  21 |     a: Integer
     |     ^
     = Member conflicts with an inherited mixin member: com.amazon.example#Mixin1$a

FAILURE: Validated 211 shapes (ERROR: 1)

This example shows that we should probably create an abstraction to contains the ValidationEvents instead of just using a raw List.

EDIT

After the recent change made by Michael this error show up in the output since now the validation events are processed in a different way, however we're still not sending those to the listener, so I think is still worth patching.

[mtdowling]

Fix extra line then ship

[mtdowling]

nit - extra line

[sugmanue]

Fixed and merged, thanks.