StdResult and StdError as anyhow alias

[Alenar]

Content

This heart of this PR is to change what StdResult and StdError are aliasing to, replacing std types with the one from anyhow:

 /// Generic error type
-pub type StdError = Box<dyn Error + Sync + Send>;
+pub type StdError = anyhow::Error;
 
 /// Generic result type
-pub type StdResult<T> = std::result::Result<T, StdError>;
+pub type StdResult<T> = anyhow::Result<T, StdError>;

Most of the other changes are related to adapting the code to anyhow results.

This PR also:

• Changes the return types of the main function of our three binaries (aggregator, signer, client) to the "new" StdResult.
  This is an improvement since when main function yield an anyhow error, it is printed out nicely (including the backtrace, see this rust playground).
• It unify the usages of boxed errors, replacing most usage of local error/result types to a StdError or StdResult.

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • Update README file (if relevant)
  • Update documentation website (if relevant)
  • Add dev blog post (if relevant)

Comments

The unused dependency to lazy_static from mithril-common was removed. It was only used to access the .deref() method something that the standard rust library already provide.

Issue(s)

Relates to #798

[github-actions]

Test Results

    3 files  ±0    17 suites  ±0   6m 35s ⏱️ +6s
666 tests ±0  666 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
722 runs  ±0  722 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit bbf4ba9. ± Comparison against base commit c07f297.

♻️ This comment has been updated with latest results.

[dlachaume]

LGTM 🚀