fix(logging): update log_class to log_group_class in CloudWatch agent configuration (#5073)

### Description
CloudWatch agent config stored in SSM used log_class inside each
collect_list entry. The agent’s JSON schema only allows log_group_class
there, so validation failed with “Additional property log_class is not
allowed” and runner user-data exited before the GitHub runner started
([issue
#5065](#5065)).

This PR maps the Terraform log_class value to log_group_class in the
serialized logfiles blob passed to cloudwatch_config.json, and updates
loggroups_classes to read log_group_class from local.logfiles so
aws_cloudwatch_log_group behavior stays aligned.

## Related Issues

Fixes
[#5065](#5065)

Author: Noah-mh

modules/runners/logging.tf

@@ -33,19 +33,20 @@ locals {
       }
     ]
   )
+  # CloudWatch agent collect_list schema expects log_group_class, not log_class
   logfiles = var.enable_cloudwatch_agent ? [for l in local.runner_log_files : {
     "log_group_name" : l.prefix_log_group ? "/github-self-hosted-runners/${var.prefix}/${l.log_group_name}" : "/${l.log_group_name}"
     "log_stream_name" : l.log_stream_name
     "file_path" : l.file_path
-    "log_class" : l.log_class
+    "log_group_class" : l.log_class
   }] : []
 
   loggroups_names = distinct([for l in local.logfiles : l.log_group_name])
   # Create a list of unique log classes corresponding to each log group name
   # This maintains the same order as loggroups_names for use with count
   loggroups_classes = [
     for name in local.loggroups_names : [
-      for l in local.logfiles : l.log_class
+      for l in local.logfiles : l.log_group_class
       if l.log_group_name == name
     ][0]
   ]