feat(simple): remove Default & 'static requirement with async-scoped feature

[beckend]

#12

• This now means that Default is a breaking change if they relied on:
  AsyncDropper::default(), Default::default(), #[derive(Default)].
  It's a trade off where you can use any Struct without Default but lose the convenience with the above. If the user as a big struct, this crate becomes a hassle to use, with this change, they have to use new or with_timeout and not rely on Default and having no need to define it.
• Timeout fixed and tested.
• 'static lifetime requirement is gone.
• inner(), inner_mut(), Deref, DerefMut available and tested.
• Derive #[derive(Debug, PartialEq, Eq, Hash, Clone)] If T allows, easier to store this struct in other structs.

[t3hmrman]

Thanks for putting out this PR @beckend 🙇

The code looks great, and I certainly learned about async-scoped today!

One non-code thing -- would you mind using Conventional Commits for your commit message? Something like feat(simple): remove Default & 'static requirement with async-scoped feature would probably represent this well (feel free to adjust that)

[beckend]

I personally copied the code as my own module, I also have 2 versions. This one and one with Default intact.
Honestly I am not going to use this module, I am using my own version.

I did this PR as a suggestion, it's fully open to be modified by you before merge.
It's your library, I think just pick out things you like or not, this is merely a suggestion of code.

[beckend]

Make your decision and I can adjust. Personally I think that static lifetime should not be required as demonstrated in the comments and tests.

[t3hmrman]

Thanks for implementing the changes -- going to take another look and figure out how to merge this work in -- thank you!

[t3hmrman]

Hey @beckend I figured out how I'm going to merge in these changes -- I've split up the fixes into separate PRs:

• Add inner(), inner_mut(), Deref impl, DerefMut impl
• Use async-scoped to remove 'static requirement
• Introduce non-default bounds via feature flag
• Fix timeout usage

This makes them a bit easier for me to understand personally -- the only one I haven't implemented yet is the non-default bounds, should have that PR upfairly soon as well.

I've put you as a co-author on all the commits, thank you again for the improvements!

[t3hmrman]

Closing out this PR since the changes that were in here have made it into 0.2.6:

https://github.com/t3hmrman/async-dropper/releases/tag/async-dropper-simple-v0.2.6