* Use Instant::now instead of duration
* Use Some
* add custom serde for Instant
* fix linter
* only enable TimeFeedback when std flag is enabled
* fix typo
* fix linter std
* cargo fmt
* allow clippy::trivially_copy_pass_by_ref on custom serde serialize function
* allow TimeObserver and Timefeedback for no_std
* cargo fmt
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Co-authored-by: Andrea Fioraldi <andreafioraldi@gmail.com>