SCHED-1071: Local NVMe support

[ali-sattari]

Add support for (raw) local NVMe disks.

[theyoprst]

couple of things:

1. cloud_init.yaml.tftpl - mdadm --create without --force may hang on recycled nodes with existing superblocks. consider running wipefs -a on each disk before creating the array, or pass --force

2. cloud_init.yaml.tftpl:136 - NVMe detection via nvme list + awk is fragile across tool versions. lsblk -d -n -o NAME,TRAN | awk '$2=="nvme" {print "/dev/"$1}' would be more reliable

3. cloud_init.yaml.tftpl:153 - hard fail on DISK_COUNT < 2. is 2+ disks guaranteed for all supported presets? if a single-disk config is possible, could just format directly without mdadm

4. cloud_init.yaml.tftpl:210 - mount_path interpolated without quoting in runcmd: prepare-disks.sh ${local_nvme_mount_path}. minor since paths are validated, but quoting is cheap

5. flux_release_nodesets.tf:29-37 / main.tf:148-155 - source_type, host_path, filesystem_type fields added to jail_submounts but only used in the nodesets template path. the source_type == "host_path" branch in the template is dead code today. is this pre-work for a future PR? if so, might be cleaner to defer

6. no validation that local_nvme.mount_path doesn't collide with other jail submount paths or system mounts

otherwise looks solid - good validation chain, init container mount checks, and per-nodeset design is clean