chore(gpu): initialize some arrays to 0

[agnesLeroy]

closes: please link all relevant issues

PR content/description

Check-list:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• Relevant issues are marked as resolved/closed, related issues are linked in the description
• Check for breaking changes (including serialization changes) and add them to commit message following the conventional commit specification

[bbarbakadze]

We don't need all of those memsets but for clarity and for code to be more robust it is good to have.
It couldn't affect benchmarks, so it's good to go.