Add tracing crate

[joshka]

Fixes #706

🎉 Hi and welcome! Please read the text below and remove it - Thank you! 🎉

No worries if anything in these lists is unclear. Just submit the PR and ask away! 👍

---

Things to check before submitting a PR

• the tests are passing locally with cargo xtask test all
  (These are failing in an unrelated way on the master branch)
• commits are squashed into one and rebased to latest master
• PR contains correct "fixes #ISSUE_ID" clause to autoclose the issue on PR merge
  • if issue does not exist consider creating it or remove the clause
• non rendered items are in sorted order (links, reference, identifiers, Cargo.toml)
• links to docs.rs have wildcard version https://docs.rs/tar/*/tar/struct.Entry.html
  • canonical link is /latest rather than /*
• example has standard error handling
  • None required
• code identifiers in description are in hyperlinked backticks

[`Entry::unpack`]: https://docs.rs/tar/*/tar/struct.Entry.html#method.unpack

Things to do after submitting PR

• check if CI is happy with your PR

[joshka]

Local failures:

error[E0119]: conflicting implementations of trait `Trait` for type `(dyn Send + Sync + 'static)`
  --> /Users/joshka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/traitobject-0.1.0/src/impls.rs:72:1
   |
71 | unsafe impl Trait for ::std::marker::Send + Sync { }
   | ------------------------------------------------ first implementation here
72 | unsafe impl Trait for ::std::marker::Send + Send + Sync { }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Send + Sync + 'static)`

error[E0119]: conflicting implementations of trait `Trait` for type `(dyn Send + Sync + 'static)`
  --> /Users/joshka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/traitobject-0.1.0/src/impls.rs:73:1
   |
71 | unsafe impl Trait for ::std::marker::Send + Sync { }
   | ------------------------------------------------ first implementation here
72 | unsafe impl Trait for ::std::marker::Send + Send + Sync { }
73 | unsafe impl Trait for ::std::marker::Sync + Send { }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Send + Sync + 'static)`

error[E0119]: conflicting implementations of trait `Trait` for type `(dyn Send + Sync + 'static)`
  --> /Users/joshka/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/traitobject-0.1.0/src/impls.rs:75:1
   |
71 | unsafe impl Trait for ::std::marker::Send + Sync { }
   | ------------------------------------------------ first implementation here
...
75 | unsafe impl Trait for ::std::marker::Sync + Send + Sync { }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Send + Sync + 'static)`

For more information about this error, try `rustc --explain E0119`.
error: could not compile `traitobject` (lib) due to 3 previous errors
warning: build failed, waiting for other jobs to finish...

This seems to be from a version of log4rs which is really old

[AndyGauge]

love it. I wonder why ci doesn't find the new crate.

[joshka]

love it. I wonder why ci doesn't find the new crate.

I think it's some random skeptic bug, but I'm not 100% sure. Perhaps if you consider #737 as a reasonable approach, I can skip to that with this PR instead?