Fix #3173 trim warning for Constant Class

[peterrsongg]

Description

ConstantClass's Intern method is not trim compatible because we cannot guarantee that the object returned by GetType() will have its public fields untrimmed, which LoadFields expects. Since we cannot directly annotate System.GetType(), we have to apply the DynamicallyAccessedMembers attribute to ConstantClass itself to guarantee that LoadFields will receive an object with its public fields untrimmed.

Motivation and Context

Fixes #3173.

Testing

DRY_RUN successful
I created a simple console app with trimming enable and then ran dotnet publish --sc -f net8.0 and the warning went away.

using Amazon;
using Amazon.SimpleSystemsManagement;
using Amazon.SimpleSystemsManagement.Model;

using (var simpleSystemsManagementClient = new AmazonSimpleSystemsManagementClient(RegionEndpoint.USWest2))
{
    var putResponse = await simpleSystemsManagementClient.PutParameterAsync(new PutParameterRequest()
    {
        Name = "something",
        Value = "something",
        Type = ParameterType.String,
        Overwrite = true,
    }).ConfigureAwait(false);
    var getParameterRequest = new GetParameterRequest()
    {
        Name = "something",
        WithDecryption = true,
    };
    var getParameterResponse = await simpleSystemsManagementClient.GetParameterAsync(getParameterRequest).ConfigureAwait(false);
}

Screenshots (if appropriate)

Types of changes

• Bug fix (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 change)

Checklist

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

• I confirm that this pull request can be released under the Apache 2 license