Implement PartitionUpdateGenerator for partial updates

Implement the logic in PartitionUpdateGenerator. Here's the summary,
1. finds the a/b partitions (both static & dynamic) on the device

For partitions not included in the payload:
2. calculates the partition hash for filesystem verification
3. generates one SOURCE_COPY operation for each static partition

The order of the partitions are sorted. So the update will resume from
the correct operation in case it's interruptted.

Bug: 157778739
Test: run a partial OTA with boot & system_ext
Change-Id: I5683b85e3c6dab813a33d5144aceb996fd8163d4
diff --git a/Android.bp b/Android.bp
index 59d698d..a5223c7 100644
--- a/Android.bp
+++ b/Android.bp
@@ -123,15 +123,16 @@
         "libbz",
         "libbspatch",
         "libbrotli",
+        "libc++fs",
         "libfec_rs",
         "libpuffpatch",
         "libverity_tree",
     ],
     shared_libs: [
-        "libziparchive",
         "libbase",
         "libcrypto",
         "libfec",
+        "libziparchive",
     ],
 }
 
@@ -731,6 +732,7 @@
         "payload_consumer/file_descriptor_utils_unittest.cc",
         "payload_consumer/file_writer_unittest.cc",
         "payload_consumer/filesystem_verifier_action_unittest.cc",
+        "payload_consumer/partition_update_generator_android_unittest.cc",
         "payload_consumer/postinstall_runner_action_unittest.cc",
         "payload_consumer/verity_writer_android_unittest.cc",
         "payload_consumer/xz_extent_writer_unittest.cc",