Boot: Make BootExecutableReader's constructor take a std::vector by value

This allows avoiding two copies of the executable data being created in
the following scenario (using pseudocode):

some_function()
{
  std::vector<u8> data = ...;
  DolReader reader{data};

  ...
}

In this scenario, if we only use the data for passing it to DolReader,
then we have to perform a copy, as the constructor takes the std::vector
as a constant reference -- you cannot move from a constant reference,
and so we copy data into the DolReader, and perform another copy in the
constructor itself when assigning the data to the m_bytes member
variable. However, we can do better.

Now, the following is allowable as well:

some_function()
{
  std::vector<u8> data = ...;
  DolReader reader{std::move(data)};

  ...
}

and now we perform no copy at any point in the reader's construction, as
we just std::move the data all the way through to m_bytes.

In the case where we *do* want to keep the executable data around after
constructing the reader, then we can just pass the vector without
std::move-ing it, and we only perform a copy once (as we'll std::move
said copy into m_bytes). Therefore, we get a more flexible interface
resource-wise out of it.

Source/Core/Core/Boot/ElfReader.cpp

@@ -68,7 +68,7 @@ static void byteswapSection(Elf32_Shdr& sec)
   bswap(sec.sh_type);
 }
 
-ElfReader::ElfReader(const std::vector<u8>& buffer) : BootExecutableReader(buffer)
+ElfReader::ElfReader(std::vector<u8> buffer) : BootExecutableReader(std::move(buffer))
 {
   Initialize(m_bytes.data());
 }