use float 16 in causal mask and masked bias
Author: hwijeen
Pull request: yes

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Fixes #13193  (issue). Problem description and reproducer is provided in the issue.


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Comments:
Pinging @jdemouth and @novatig 

@novatig it looks good to me. Are you ok with the changes? 

@hwijeen and @LysandreJik, sorry for the delay, I was on holidays ;)

No worries, thanks for taking a look! :)

This is a kindly reminder for @novatig :)

Merging since @jdemouth approved - will reverse if @novatig disagrees.

Sorry all, I did not see the notification in my inbox and it slipped my mind.

A very belated LGTM