feat: support rust 1.81.0 (#9139)
### Description
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- features `fs_try_exists` and `panic_info_message` are stable
- fs::try_exists is now fs::exists
- PanicInfo is now PanicHookInfo (use `to_string` method for it)
- switch to 1.81.0-nightly in rust-toolchain.toml
### Testing Instructions
`cargo test` to ensure the code has the same behavior as before
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