logd: replace std::vector<uint8_t> in SerializedLogChunk

Turns out std::vector::resize() and std::vector::clear() don't
actually deallocate any memory.  std::vector::shrink_to_fit() can be
used for this but isn't a 'guarantee'.  Instead of trying to get
std::vector to play nice, this change replaces std::vector<uint8_t>
with std::unique_ptr<uint8_t[]>, which is more accurate to how I'm
using this memory anyway.

Test: logging unit tests
Change-Id: I9638e90bbf50bcf316c5aa172c8278ea945d27e7
diff --git a/logd/CompressionEngine.h b/logd/CompressionEngine.h
index d760cea..0f760ed 100644
--- a/logd/CompressionEngine.h
+++ b/logd/CompressionEngine.h
@@ -16,8 +16,9 @@
 
 #pragma once
 
-#include <span>
-#include <vector>
+#include <memory>
+
+#include "SerializedData.h"
 
 class CompressionEngine {
   public:
@@ -25,23 +26,20 @@
 
     virtual ~CompressionEngine(){};
 
-    virtual bool Compress(std::span<uint8_t> in, std::vector<uint8_t>& out) = 0;
-    // Decompress the contents of `in` into `out`.  `out_size` must be set to the decompressed size
-    // of the contents.
-    virtual bool Decompress(const std::vector<uint8_t>& in, std::vector<uint8_t>& out,
-                            size_t out_size) = 0;
+    virtual bool Compress(SerializedData& in, size_t data_length, SerializedData& out) = 0;
+    // Decompress the contents of `in` into `out`.  `out.size()` must be set to the decompressed
+    // size of the contents.
+    virtual bool Decompress(SerializedData& in, SerializedData& out) = 0;
 };
 
 class ZlibCompressionEngine : public CompressionEngine {
   public:
-    bool Compress(std::span<uint8_t> in, std::vector<uint8_t>& out) override;
-    bool Decompress(const std::vector<uint8_t>& in, std::vector<uint8_t>& out,
-                    size_t out_size) override;
+    bool Compress(SerializedData& in, size_t data_length, SerializedData& out) override;
+    bool Decompress(SerializedData& in, SerializedData& out) override;
 };
 
 class ZstdCompressionEngine : public CompressionEngine {
   public:
-    bool Compress(std::span<uint8_t> in, std::vector<uint8_t>& out) override;
-    bool Decompress(const std::vector<uint8_t>& in, std::vector<uint8_t>& out,
-                    size_t out_size) override;
+    bool Compress(SerializedData& in, size_t data_length, SerializedData& out) override;
+    bool Decompress(SerializedData& in, SerializedData& out) override;
 };
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