Parsing should not depend on `std`

There are some instances where parsing of structs (`core::str::FromStr`) makes use of the implementations provided by the standard library. Problematically, these are defined in `std` and not in `core` such that this depends on the `std` feature. This makes the trait implementations inconsistent and makes the dependency quite a lot heavier.

Instead, such parsing should be implemented in a standalone version (possibly with a dedicated, small dependency).

尋找那些實作了 `core::str::FromStr` 但依賴 `std` 進行解析的結構體。識別哪些類型受到影響，並檢查它們當前的解析邏輯。研究小型、無標準庫（no-std）的解析 crate，或考慮實作一個最小化的解析器。透過確保 crate 在不啟用 `std` 功能時仍能建置來測試變更。

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