Extract type aliases in LtHash members

Summary: [Folly] Extract type aliases in `LtHash` members to avoid unnatural line breaks and indentation.

Reviewed By: modocache

Differential Revision: D16453375

fbshipit-source-id: 8d68458ba3ba7bf79fef82986f4f170e3b74ddd6

folly/experimental/crypto/LtHash-inl.h

@@ -336,9 +336,8 @@ LtHash<B, N>& LtHash<B, N>::addObject(
     folly::ByteRange firstRange,
     Args&&... moreRanges) {
   // hash obj and add to elements of checksum
-  alignas(detail::kCacheLineSize)
-      std::array<unsigned char, getChecksumSizeBytes()>
-          h;
+  using H = std::array<unsigned char, getChecksumSizeBytes()>;
+  alignas(detail::kCacheLineSize) H h;
   hashObject(
       {h.data(), h.size()}, firstRange, std::forward<Args>(moreRanges)...);
   detail::MathOperation<detail::MathEngine::AUTO>::add(
@@ -356,9 +355,8 @@ LtHash<B, N>& LtHash<B, N>::removeObject(
     folly::ByteRange firstRange,
     Args&&... moreRanges) {
   // hash obj and subtract from elements of checksum
-  alignas(detail::kCacheLineSize)
-      std::array<unsigned char, getChecksumSizeBytes()>
-          h;
+  using H = std::array<unsigned char, getChecksumSizeBytes()>;
+  alignas(detail::kCacheLineSize) H h;
   hashObject(
       {h.data(), h.size()}, firstRange, std::forward<Args>(moreRanges)...);
   detail::MathOperation<detail::MathEngine::AUTO>::sub(