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:

v4.0.0

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

v3.6.0

• Fix: Mark test scripts with Bash'isms to be run via Bash
• Add option to fetch tags even if fetch-depth > 0

v3.5.3

• Fix: Checkout fail in self-hosted runners when faulty submodule are checked-in
• Fix typos found by codespell
• Add support for sparse checkouts

v3.5.2

• Fix api endpoint for GHES

v3.5.1

• Fix slow checkout on Windows

v3.5.0

• Add new public key for known_hosts

v3.4.0

• Upgrade codeql actions to v2
• Upgrade dependencies
• Upgrade @actions/io

v3.3.0

• Implement branch list using callbacks from exec function
• Add in explicit reference to private checkout options
• Fix comment typos

v3.2.0

• Add GitHub Action to perform release
• Fix status badge
• Replace datadog/squid with ubuntu/squid Docker image
• Wrap pipeline commands for submoduleForeach in quotes
• Update @actions/io to 1.1.2
• Upgrading version to 3.2.0

v3.1.0

• Use @actions/core saveState and getState
• Add github-server-url input

v3.0.2

• Add input set-safe-directory

v3.0.1

• Fixed an issue where checkout failed to run in container jobs due to the new git setting safe.directory
• Bumped various npm package versions

v3.0.0

• Update to node 16

Still using v2 of actions/checkout will generate some warning like in this run: https://github.com/rustwasm/twiggy/actions/runs/4203488247

Node.js 12 actions are deprecated. Please update the following actions to use Node.js 16: actions/checkout@v2, actions-rs/cargo@v1, actions-rs/toolchain@v1. For more information see: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/.

The PR will get rid of those warnings for actions/checkout, because v3 uses Node.js 16.