ci: add crates.io publish workflow

[epilys]

Add a trusted publishing workflow for crates.io. It will be triggered everytime there's a push of a tag starting with v.

The workflow must be manually added to crates.io:

Configuring Trusted Publishing

Configure your crate on crates.io:

Go to your crate's Settings → Trusted Publishing
Click the "Add" button and fill in:
    Repository owner: Your GitHub username or organization
    Repository name: The name of your repository
    Workflow filename: The filename of your GitHub Actions workflow (e.g., "release.yml")
    Environment: Optional environment name if you're using GitHub environments
Save the configuration

Documentation: https://crates.io/docs/trusted-publishing

cc @roypat

Requirements

Before submitting your PR, please make sure you addressed the following
requirements:

• All commits in this PR have Signed-Off-By trailers (with
  git commit -s), and the commit message has max 60 characters for the
  summary and max 75 characters for each description line.
• All added/changed functionality has a corresponding unit/integration
  test.
• All added/changed public-facing functionality has entries in the "Upcoming
  Release" section of CHANGELOG.md (if no such section exists, please create one).
• Any newly added unsafe code is properly documented.

[roypat]

I've registered this workflow as a trusted publisher on crates.io, so I guess once we merge this we can give it a try with the 0.14 release that I'm suspecting cloudhypervisor will want soon for cloud-hypervisor/cloud-hypervisor#7117 (comment)

[epilys]

@roypat sounds good. Feel free to merge whenever it's necessary!