Tracking issue for deprecation of `failure` crate

[trevyn]

Per its README, the failure crate is deprecated:

Notice: failure is deprecated. If you liked failure's API, consider using:

• Anyhow is a good replacement for failure::Error.
• thiserror is a good, near drop-in replacement for #[derive(Fail)].

I agree with the suggestion to migrate to anyhow and thiserror, and will investigate it unless anyone has other suggestions or objections.

Investigating on branch https://github.com/trevyn/grin/tree/trevyn-deprecate-failure. To do:

• [x] Wait for https://github.com/mimblewimble/grin/pull/3630 or equivalent to be merged; it contains code that interacts with failure's Error/ErrorKind pattern that needs to be reworked.
• [x] Rework #[derive(Fail)] to #[derive(thiserror::Error)]
• [x] Try removing Error/ErrorKind pattern — is this still required with thiserror?

[antiochp]

I'm :+1: on exploring replacements for failure here. We have had multiple iterations of our error handling, none of which have felt 100% right. And we are definitely not the only rust project to struggle with this.

[trevyn]

PR in progress: #3633