ci: update GitHub Actions and expand package compatibility checks

[microshine]

Summary

Updates the GitHub Actions workflow and improves package compatibility testing across supported Node.js versions.

Changes

• Update GitHub Actions dependencies to their latest major versions
• Run the main CI build on Node.js 24
• Build and pack the npm package once, then reuse the generated tarball for compatibility checks
• Test the packaged artifact on Node.js 20, 22, 24, and 26
• Install the package in a clean consumer environment instead of testing directly from the repository
• Verify CommonJS consumption with require("@peculiar/x509")
• Verify ESM consumption with import("@peculiar/x509")
• Disable unnecessary npm caching in compatibility jobs
• Limit push and pull request CI runs to the master branch

Why

The compatibility job now tests the same package artifact that would be published to npm, which helps catch packaging, dependency, and runtime compatibility issues that may not be visible when running tests directly from the repository.

It also avoids rebuilding the package for every Node.js version, keeping the compatibility matrix relatively lightweight.