chore: adopt upstream OCI snapshot format

- Point hyperlight-host at upstream hyperlight-dev/hyperlight main
  (no custom branch dependencies)
- Adapt snapshot persistence to upstream OCI format (directory-based)
- Re-map initrd via map_file_cow after every restore() since file
  mappings are separate hypervisor memory regions not in the snapshot
- Reduce pyhl heap from 2560 MiB to 1280 MiB (minimum for Python
  warmup with pandas+docx)
- Remove sparsify_snapshot code (was file-format specific)
- Remove memmap2 and extra windows-sys features (no longer needed)
- Update snapshot path references from file to directory in CI, tests,
  and examples

Signed-off-by: danbugs <danilochiarlone@gmail.com>

Author: danbugs

.github/workflows/benchmarks.yml

@@ -287,9 +287,9 @@ jobs:
       - name: "Snapshot size"
         if: steps.kvm_check.outputs.available == 'true'
         run: |
-          snap=".pyhl/snapshot.hls"
-          apparent=$(($(stat -c '%s' "$snap") / 1024 / 1024))
-          disk=$(($(stat -c '%b' "$snap") * 512 / 1024 / 1024))
+          snap=".pyhl/snapshot"
+          apparent=$(($(find "$snap" -type f -exec stat -c '%s' {} + | paste -sd+ | bc) / 1024 / 1024))
+          disk=$(($(find "$snap" -type f -exec stat -c '%b' {} + | paste -sd+ | bc) * 512 / 1024 / 1024))
           echo "| Metric | Value |"
           echo "|--------|-------|"
           echo "| Apparent size | ${apparent} MiB |"
@@ -483,27 +483,10 @@ jobs:
       - name: "Snapshot size"
         shell: pwsh
         run: |
-          $snap = ".pyhl\snapshot.hls"
-          $f = Get-Item $snap
-          $apparentMiB = [math]::Round($f.Length / 1MB)
-          # GetCompressedFileSize returns actual on-disk allocation for sparse files
-          $wide = $f.FullName
-          Add-Type -TypeDefinition @"
-          using System;
-          using System.Runtime.InteropServices;
-          public class SparseHelper {
-            [DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Unicode)]
-            public static extern uint GetCompressedFileSizeW(string lpFileName, out uint lpFileSizeHigh);
-          }
-          "@ -ErrorAction SilentlyContinue
-          $high = [uint32]0
-          $low = [SparseHelper]::GetCompressedFileSizeW($wide, [ref]$high)
-          if ($low -ne [uint32]::MaxValue) {
-            $diskBytes = ([uint64]$high -shl 32) -bor [uint64]$low
-            $diskMiB = [math]::Round($diskBytes / 1MB)
-          } else {
-            $diskMiB = $apparentMiB
-          }
+          $snap = ".pyhl\snapshot"
+          $files = Get-ChildItem -Path $snap -Recurse -File
+          $apparentMiB = [math]::Round(($files | Measure-Object -Property Length -Sum).Sum / 1MB)
+          $diskMiB = $apparentMiB
           Write-Host "| Metric | Value |"
           Write-Host "|--------|-------|"
           Write-Host "| Apparent size | ${apparentMiB} MiB |"