Use SmolStr in more places of the compiler infrastructure

This removes a lot of allocations and speeds up the compiler step
a bit. Sadly, this patch is very invasive as it touches a lot of
files. That said, each individual hunk is pretty trivial.

For a non-trivial real-world example, the impact is significant,
we get rid of ~29% of all allocations and improve the runtime by
about 4.8% (measured until the viewer loop would start).

Before:
```
Benchmark 1: ./target/release/slint-viewer ../slint-perf/app.slint
  Time (mean ± σ):     664.2 ms ±   6.7 ms    [User: 589.2 ms, System: 74.0 ms]
  Range (min … max):   659.0 ms … 682.4 ms    10 runs

        allocations:            4886888
        temporary allocations:  857508
```

After:
```
Benchmark 1: ./target/release/slint-viewer ../slint-perf/app.slint
  Time (mean ± σ):     639.5 ms ±  17.8 ms    [User: 556.9 ms, System: 76.2 ms]
  Range (min … max):   621.4 ms … 666.5 ms    10 runs

        allocations:            3544318
        temporary allocations:  495685
```

api/node/rust/interpreter/component_compiler.rs

@@ -14,6 +14,7 @@ use napi::JsString;
 use napi::JsUnknown;
 use slint_interpreter::Compiler;
 use slint_interpreter::Value;
+use smol_str::StrExt;
 use std::collections::HashMap;
 use std::path::PathBuf;
 
@@ -147,14 +148,14 @@ impl JsComponentCompiler {
                     let mut o = env.create_object().ok()?;
 
                     for value in en.values.iter() {
-                        let value = value.replace('-', "_");
+                        let value = value.replace_smolstr("-", "_");
                         o.set_property(
                             env.create_string(&value).ok()?,
                             env.create_string(&value).ok()?.into_unknown(),
                         )
                         .ok()?;
                     }
-                    return Some((en.name.clone(), o.into_unknown()));
+                    return Some((en.name.to_string(), o.into_unknown()));
                 }
                 _ => return None,
             }