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/modules/crystal.rs

@@ -1,4 +1,4 @@
-use super::{Context, Module, RootModuleConfig};
+use super::{Context, Module, ModuleConfig};
 
 use crate::configs::crystal::CrystalConfig;
 use crate::formatter::StringFormatter;