chore: switch to stable toolchain

[BugenZhao]

After #153, this PR furthers replaces other minor nightly features with stable alternatives. Also removed unstable options in rustfmt.

[gemini-code-assist]

Code Review

This pull request transitions the project from a nightly Rust toolchain to a stable one by removing several nightly-only features, including trait_alias, try_blocks, and iterator_try_collect. These features are replaced with stable alternatives such as the trait-set and itertools crates, and by refactoring try blocks into async blocks or standard error handling. Additionally, the toolchain and formatting configurations have been updated to reflect this shift. Feedback includes a correction for the specified Rust version in rust-toolchain.toml, which is currently set to a non-existent version, and a suggestion to use supertraits instead of the trait-set dependency to avoid compiling multiple versions of syn and to simplify the dependency tree.