Update actions/checkout in GitHub Actions workflows to v4

[striezel]

Updates the actions/checkout action used in the GitHub Actions workflows to its newest major version.

Changes in actions/checkout:

v4.1.0

• Add support for partial checkout filters

v4.0.0

• Support fetching without the --progress option
• Update to node20

Still using v3 of actions/checkout will generate some warning like in this run: https://github.com/rustwasm/wasm-bindgen/actions/runs/7804982319

Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v3. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

The PR will get rid of those warnings for actions/checkout, because v4 uses Node.js 20.

[daxpedda]

Thank you!