Release `Version 3.0.1` (#1190)

* Bump `ink_lang_codegen` crate to `v3.0.1`

* Actually, don't bump in `ink_lang_macro`

* Bump to version `3.0.1`

* Add release notes

* Add section for `examples/` release procedure

* Add some details to release checklist

* Move `Version 3.0.1` out of `Unreleased`

* More updates to the release checklist

* Mark all examples as `publish = false`

* Make release notes consistent with old releases

Co-authored-by: Michael Müller <mich@elmueller.net>

* Add mention to `crates.io`

* `package.publish` value shouldn't be a string

* Update RELEASES_CHECKLIST.md

* Update RELEASES_CHECKLIST.md

Co-authored-by: Michael Müller <mich@elmueller.net>