Reduce usage of String in translations code.

[CosminPerRam]

This is a part of #523 (the non-lint part of it).
This PR removes an unnecessary to_string call on an already String value and replaces per-item .to_string() with an entire match block .to_string().

[GyulyVGC]

Thanks!

While you are at it, would you mind updating all the translations methods to return an &'static str?

I think there are some cases where I actually don't need them to be strings, so this should be more efficient.

In cases Strings are actually needed, it'd be nice updating the code where the function is invoked calling .to_string() and leaving &str as return value of the method.

[CosminPerRam]

Although there is a mix usage of &'static str, String and Text<'static, StyleType>, I ought here to replace only the non-parameter-composing String instances as replacing Text ones would require bigger changes (that can be done in another PR).

[GyulyVGC]

Although there is a mix usage of &'static str, String and Text<'static, StyleType>, I ought here to replace only the non-parameter-composing String instances as replacing Text ones would require bigger changes (that can be done in another PR).

I agree, and I'm fine with this.