Update to the latest Linebender CI standard.

[xStrom]

• The CI script gets a big update to bring it more in sync with the latest standard.
• piet-common loses the web feature, which was functionally broken anyway as shown by the new CI.
  The piet-web backend was and still is automatically chosen when targeting wasm32.
• Enable the doc_auto_cfg feature for docs.rs which will show a little tip next to feature gated functionality informing of the crate feature flag.
• Piet version is now configured in the workspace Cargo.toml instead of all over the place.
• Cargo.lock is now committed.
• Piet now has an explicit MSRV of 1.77 and it's documented.
• Each published package now has its own copy of the license files.