refactor: replace module_config_derive with serde (#3786)

* refactor: replace module_config_derive with serde

Changes include:
* Removing `starship_module_config_derive` and replacing it with `serde::Deserialize`
* Removing `RootModuleConfig::load_config`. While potentially useful, it was only used in tests. And it would require something like `serde::DeserializeSeed` which is not derived by serde.
* Merging `RootModuleConfig` into `ModuleConfig`
* Implementing a `ValueDeserializer` that holds a reference to a `toml::Value` in `serde_utils.rs`
* Deserialization errors (invalid type) are now logged and include the current key and the struct names
* Unknown keys are now considered an error. "Did you mean?"-messages are still possible

* fix typo

Co-authored-by: Matan Kushner <hello@matchai.dev>

Co-authored-by: Matan Kushner <hello@matchai.dev>

src/lib.rs

@@ -18,6 +18,7 @@ pub mod module;
 mod modules;
 pub mod print;
 mod segment;
+mod serde_utils;
 mod utils;
 
 #[cfg(test)]