Everywhere: Convert ByteBuffer factory methods from Optional -> ErrorOr

Apologies for the enormous commit, but I don't see a way to split this
up nicely. In the vast majority of cases it's a simple change. A few
extra places can use TRY instead of manual error checking though. :^)

Userland/Libraries/LibGfx/BMPLoader.cpp

@@ -927,7 +927,7 @@ static bool uncompress_bmp_rle_data(BMPLoadingContext& context, ByteBuffer& buff
         return false;
     }
     auto buffer_result = ByteBuffer::create_zeroed(buffer_size);
-    if (!buffer_result.has_value()) {
+    if (buffer_result.is_error()) {
         dbgln("Not enough memory for buffer allocation");
         return false;
     }