feat: add Trunc op

[mooori]

Adds the Trunc op for burn#3768.

On a x86 Linux machine with AMD GPU cargo xtask test --ci passes. I don't have access to an Nvidia GPU and also no HIP setup. Is there any infra to run tests on all supported platforms and runtimes?

If I merged the latest main branch of cubecl, then cargo run-checks in burn runs into compilation errors.

Instructions

• Create a new branch or fork of the burn repo
• Update the main Cargo.toml with this PR hash.
• Fix any broken tests or compilation errors in burn.
•  Submit a PR in burn with your fixes and link it here.

Here is the PR in burn.

[laggui]

LGTM!

Should be able to merge the latest main changes and update the rev in burn now that the small breaking changes have been merged in burn.