CUDA GreedySearch ProcessLogits optimization (#13823)
### Description
Explore the possible re-use of the logits buffer in `GreedySearch` for
cases where sequence length == 1 (Post the first decoding run, the
sequence length is guaranteed to be 1). This re-use will ensure that we
do not have to make copies of the logits before processing them.
Currently, we make a copy of the logits even if the sequence length == 1
which is not necessary as we can directly re-use the logits buffer for
the token generation step. A similar optimization exists in
`BeamSearch`, but seems lacking in `GreedySearch`. Since, the logits
buffer may contain padded data, we need to adjust the pieces consuming
the logits buffer directly to account for any padding.
A more invasive change (needs changes in a few places) will be to adjust
the interfaces of `ProcessLogits()` such that it takes a reference to
the logits and not a const reference as (based on my understanding) this
is the only place where the logits from the decoder subgraph will ever
be used and giving the `ProcessLogits()` method license to
mutate/process the underlying buffer of the logits OrtValue seems
reasonable (instead of making a copy and then mutating/processing them).
The will also remove the ugly `const_cast`(s) seen in this change.
