fix(runner): handle long prefixes in pool scheduler and IAM resource names (#5139)

The pool module's `aws_scheduler_schedule_group` and `aws_iam_role` for
the scheduler both use `name_prefix`, which has a 38-character limit (64
max name minus 26 for Terraform's random suffix). When the module prefix
is long — for example a multi-runner prefix like
`self-hosted-linux-ubuntu2404-x64-2cpu-8gb` — the combined
`${prefix}-pool` exceeds 38 characters and Terraform fails.

For long prefixes, the name is now truncated with an md5 hash suffix to
stay within limits, matching the existing pattern used elsewhere in the
module. Existing deployments with short prefixes see no resource
changes.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: alexjurkiewicz

modules/runners/pool/main.tf

@@ -1,3 +1,11 @@
+locals {
+  pool_name_prefix = (
+    length("${var.config.prefix}-pool") <= 38
+    ? "${var.config.prefix}-pool"
+    : "${substr("${var.config.prefix}-pool", 0, 29)}-${substr(md5("${var.config.prefix}-pool"), 0, 8)}"
+  )
+}
+
 resource "aws_lambda_function" "pool" {
 
   s3_bucket                      = var.config.lambda.s3_bucket != null ? var.config.lambda.s3_bucket : null
@@ -157,7 +165,7 @@ resource "aws_iam_role_policy" "pool_xray" {
 }
 
 resource "aws_scheduler_schedule_group" "pool" {
-  name_prefix = "${var.config.prefix}-pool"
+  name_prefix = local.pool_name_prefix
 
   tags = var.config.tags
 }
@@ -188,7 +196,7 @@ data "aws_iam_policy_document" "scheduler" {
 }
 
 resource "aws_iam_role" "scheduler" {
-  name_prefix = "${var.config.prefix}-pool"
+  name_prefix = local.pool_name_prefix
 
   path                 = var.config.role_path
   permissions_boundary = var.config.role_permissions_boundary