Implements a specialized constructor `LanguageName::new_static` for
`&'static str` which reduces allocations.

`LanguageName::new` always backs the underlying `SharedString` with an
owned `Arc<str>` even when a `&'static str` is passed. This makes us
allocate each time we create a new `LanguageName` no matter what.
Creating a specialized constructor for `&'static str` allows us to
essentially construct them for free.

Additional change:
Encourages using explicit constructors to avoid needless allocations.
Currently there were no instances of this trait being called where the
lifetime was not `'static` saving another 48 locations of allocation.

```rust
impl<'a> From<&'a str> for LanguageName {
    fn from(str: &'a str) -> Self {
        Self(SharedString::new(str))
    }
}

// to 

impl From<&'static str> for LanguageName {
    fn from(str: &'static str) -> Self {
        Self(SharedString::new_static(str))
    }
}

```

Release Notes:

- N/A