Fix compile error due to missing header

[ttnghia]

Some recently merged PRs (#11018 + #11036) do not include enough header which may cause compile error in some systems (in particular, CUDA 11.7 + gcc-11.2). This PR adds the missing header (<optional>) to fix the compile issue.

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@@               Coverage Diff               @@
##             branch-22.08   #11126   +/-   ##
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[karthikeyann]

LGTM 👍

[ttnghia]

@gpucibot merge