chore(orch): split mkfs.ext4 feature flags into individually commentable slice

Replace the single comma-separated string literal for mkfs.ext4 -O with
strings.Join over a slice, so each ext4 feature flag can be commented
individually. Flags are sorted alphabetically within the main group,
with ^orphan_file separated at the end as a guest-compatibility workaround.

Original comments describing the feature set rationale (tar2ext4 matching,
kept defaults, orphan_file compat) are preserved in place.

No functional change - produces the identical argument string at runtime.

Addresses review feedback from #2082.

Link: #2082 (comment)

Author: arkamar

packages/orchestrator/internal/template/build/core/filesystem/ext4.go

@@ -41,14 +41,28 @@ func Make(ctx context.Context, rootfsPath string, sizeMb int64, blockSize int64)
 
 	cmd := exec.CommandContext(ctx,
 		"mkfs.ext4",
-		// Matches the final ext4 features used by tar2ext4 tool
-		// But enables resize_inode, sparse_super (default, required for resize_inode), has_journal (default), metadata_csum (default).
-		// orphan_file is disabled (added as default in e2fsprogs >= 1.47.0) to ensure guest e2fsprogs tools
-		// (tune2fs, resize2fs, e2fsck) from older images (e.g. Ubuntu 22.04, Debian 11) can write to
-		// the filesystem. Without this, any write operation from the guest fails with "unsupported
-		// read-only feature(s)" when the host e2fsprogs is newer than the guest's.
-		// See https://e2fsprogs.sourceforge.net/e2fsprogs-release.html#1.47.0
-		"-O", `^dir_index,^64bit,^dir_nlink,^orphan_file,ext_attr,sparse_super2,filetype,extent,flex_bg,large_file,huge_file,extra_isize`,
+		"-O", strings.Join([]string{
+			// Matches the final ext4 features used by tar2ext4 tool.
+			// But enables resize_inode, sparse_super (required for resize_inode),
+			// has_journal, and metadata_csum are kept as defaults.
+			"^64bit",
+			"^dir_index",
+			"^dir_nlink",
+			"ext_attr",
+			"extent",
+			"extra_isize",
+			"filetype",
+			"flex_bg",
+			"huge_file",
+			"large_file",
+			"sparse_super2",
+
+			// Disabled for compatibility with older guest e2fsprogs (Ubuntu 22.04, Debian 11).
+			// orphan_file was added as default in e2fsprogs >= 1.47.0; without disabling it,
+			// guest tools fail with "unsupported read-only feature(s)".
+			// See https://e2fsprogs.sourceforge.net/e2fsprogs-release.html#1.47.0
+			"^orphan_file",
+		}, ","),
 		"-b", strconv.FormatInt(blockSize, 10),
 		"-m", strconv.FormatInt(reservedBlocksPercentage, 10),
 		"-i", strconv.FormatInt(inodesRatio, 10),