ComputeCanada/magic_castle: Magic Castle 15.2.0

Added Added crashkernel=0M to kernel args (PR #391) Added tags to incus instance description (PR #401) Changed Fixed issue #396 "Error when using pool instance with incus provider" (PR #397) Fixed issue #399 "PR #388 introduced a regression when using commit hash with config_version" (PR #402) Enabled incus security.nesting when privileged is enabled (PR #400) Improved cloud-init failure handling (PR #403) Fixed validation to allow var.instances to be an empty map (PR #405) Limited dkim record to 255 characters per chunk (Issue #408, PR #409)