This reverts commit 0c99ba1eab63865592bb084feb271cd4e4b0357e, reversing
changes made to 5f92b070bf284f1493b1b5d433dd3adde2f46727.
This caused a CI failure when it landed in master branch due to a
128-bit `@byteSwap` in std.mem.
Closes#16861
Using `alloc_if_needed` when parsing a `Value` allows receiving a token
which points to the buffer of the underlying `Reader`. This token will
no longer be valid after the `Reader`'s buffer is refilled, which will
happen with large values. Using `alloc_always` avoids this issue by
ensuring the returned tokens always own their data independently of the
underlying buffer.
