Add the links field to the Cargo manifest of esp-println and potentially other packages

[jessebraham]

It's currently possible to accidentally include multiple versions of esp-println in your project, which results in compilation errors when the build script is performing the feature verification.

This should be resolvable by simply adding links = "esp-println" to esp-println/Cargo.toml under the [package] section.

Additionally, we should evaluate which, if any, other packages should receive this change, and update all relevant packages.

[jessebraham]

@bjoernQ I'm not sure any other packages really need it at this point, can you think of any? If not I'll add this field and close this issue.

[bjoernQ]

@bjoernQ I'm not sure any other packages really need it at this point, can you think of any? If not I'll add this field and close this issue.

I don't think any other package needs it - thanks for taking care of this