add Huawei Bootloader packed image format (kaitai-io#459)

* add Huawei Bootloader packed image format

* huawei boot image: introduce version type, rewrite entries

* android_img_huawei: rename to `android_bootldr_huawei`

... per the same naming convention as used for
kaitai-io#471

* android_bootldr_huawei: shorten commit hash

* android_bootldr_huawei: fix format description, link to samples

* android_bootldr_huawei: fix indentation

* android_bootldr_huawei: take `meta_hdr_sz` into account, rename headers

* android_bootldr_huawei: make `image_version` a string, ASCII enc

* android_bootldr_huawei: parse `body` in `image_hdr_entry`, rename fields

* android_bootldr_huawei: add info where all factory images are

Co-authored-by: Petr Pucil <[email protected]>

archive/android_bootldr_huawei.ksy

@@ -0,0 +1,81 @@
+meta:
+  id: android_bootldr_huawei
+  title: Huawei Bootloader packed image format
+  file-extension: img
+  tags:
+    - archive
+    - android
+  license: CC0-1.0
+  # The `releasetools.py` script is written for Python 2, where the default
+  # encoding is ASCII.
+  encoding: ASCII
+  endian: le
+doc: |
+  Format of `bootloader-*.img` files found in factory images of certain Android devices from Huawei:
+
+  * Nexus 6P "angler": [sample][sample-angler] ([other samples][others-angler]),
+    [releasetools.py](https://android.googlesource.com/device/huawei/angler/+/cf92cd8/releasetools.py#29)
+
+  [sample-angler]: https://androidfilehost.com/?fid=11410963190603870158 "bootloader-angler-angler-03.84.img"
+  [others-angler]: https://androidfilehost.com/?w=search&s=bootloader-angler&type=files
+
+  All image versions can be found in factory images at
+  <https://developers.google.com/android/images> for the specific device. To
+  avoid having to download an entire ZIP archive when you only need one file
+  from it, install [remotezip](https://github.com/gtsystem/python-remotezip) and
+  use its [command line
+  tool](https://github.com/gtsystem/python-remotezip#command-line-tool) to list
+  members in the archive and then to download only the file you want.
+
+doc-ref: https://android.googlesource.com/device/huawei/angler/+/673cfb9/releasetools.py
+seq:
+  - id: meta_header
+    type: meta_hdr
+  - id: header_ext
+    size: meta_header.len_meta_header - meta_header._sizeof
+  - id: image_header
+    size: meta_header.len_image_header
+    type: image_hdr
+types:
+  meta_hdr:
+    seq:
+      - id: magic
+        contents: [0x3c, 0xd6, 0x1a, 0xce]
+      - id: version
+        type: version
+      - id: image_version
+        size: 64
+        type: strz
+      - id: len_meta_header
+        -orig-id: meta_hdr_sz
+        type: u2
+      - id: len_image_header
+        -orig-id: img_hdr_sz
+        type: u2
+  version:
+    seq:
+      - id: major
+        type: u2
+      - id: minor
+        type: u2
+  image_hdr:
+    seq:
+      - id: entries
+        type: image_hdr_entry
+        repeat: eos
+  image_hdr_entry:
+    -webide-representation: '{name} - o:{ofs_body}, s:{len_body}'
+    seq:
+      - id: name
+        size: 72
+        type: strz
+        doc: partition name
+      - id: ofs_body
+        type: u4
+      - id: len_body
+        type: u4
+    instances:
+      body:
+        io: _root._io
+        pos: ofs_body
+        size: len_body