Dump debug information for apply_patch unit tests

The apply patch test should have a deterministic way to append patch
data. Add debug logs to dump the length and SHA1 of each step to further
track down the flakiness.

Also redirect the debug logging to stdout in case the logcat becomes too
chatty.

Bug: 67849209
Test: Run recovery_component_test
Change-Id: I42bafef2d9dee599719ae57840b3d8c00d243ebd

applypatch/applypatch.cpp

@@ -630,6 +630,11 @@ static int GenerateTarget(const FileContents& source_file, const std::unique_ptr
   SHA_CTX ctx;
   SHA1_Init(&ctx);
   SinkFn sink = [&memory_sink_str, &ctx](const unsigned char* data, size_t len) {
+    if (len != 0) {
+      uint8_t digest[SHA_DIGEST_LENGTH];
+      SHA1(data, len, digest);
+      LOG(DEBUG) << "Appending " << len << " bytes data, sha1: " << short_sha1(digest);
+    }
     SHA1_Update(&ctx, data, len);
     memory_sink_str.append(reinterpret_cast<const char*>(data), len);
     return len;