ci: replace deprecated GitHub Actions with modern equivalents

[abhi0324]

Problem

integration.yml and release.yml use several deprecated and unmaintained GitHub Actions that produce warnings on every CI run:

Action	Status
actions-rs/toolchain@v1	archived, unmaintained
actions-rs/cargo@v1	archived, unmaintained
actions/checkout@v2	outdated, v4 is current
actions/upload-artifact@v2	outdated, v4 is current
Swatinem/rust-cache@v1	outdated, v2 is current

Notably lint.yml already uses dtolnay/rust-toolchain@stable correctly - this PR brings the other two workflows in line with it.

Changes

integration.yml

• actions-rs/toolchain@v1 → dtolnay/rust-toolchain@stable

release.yml

• actions/checkout@v2 → actions/checkout@v4
• actions-rs/toolchain@v1 → dtolnay/rust-toolchain@stable
• Swatinem/rust-cache@v1 → Swatinem/rust-cache@v2
• actions-rs/cargo@v1 → direct cargo build run command
• actions/upload-artifact@v2 → actions/upload-artifact@v4

Testing

• integration.yml - runs automatically on this PR, results visible in the Actions tab above.
• release.yml - tag-only workflow, cannot be triggered by a PR. Changes are mechanical replacements verified against the already-working pattern in lint.yml, which uses dtolnay/rust-toolchain@stable successfully.

Notes

• The targets: parameter replaces target: for dtolnay/rust-toolchain
• actions-rs/cargo replaced with a direct run: step - the recommended approach that removes an unnecessary dependency
• No behaviour changes - all steps perform identical operations

[fahdfady]

you sure about target -> targets?

[viferga]

He's trying to inject malicious js into our repository.