Update dependencies and minor fixes

[rchildre3]

• Use dependabot to keep dependencies up-to-date, fairly lax monthly schedule, can update to be more frequent, if necessary.
• Example testcase suggests grammar which will never find coverage (xml) generator. move to the regex mutator to at least find something.
• serde_derive crate is now a feature of the main serde crate.
  • Add necessary use statements
• Update Snafu types and generated types
• fork() is an unsafe function
• Use chrono crate instead of time crate. As getting the system time in a multi-threaded application became significantly more annoying with the commits here and here. Whereas chrono does not need these configuration parameters. And easy to use a single dependency everywhere where time formatting is needed.
• Update clap to new 4.0 APIs
• Various clippy warnings
• Fix regression in recent .len() > 0 refactorings, boolean flipped in:
  • grammartec/src/tree.rs
• Unpin nightly from a specific daily version of nightly. Most Rust developers keep a floating nightly install. Requiring an exact toolchain per project clutters installed toolchains and not trivial to chase down what project need what exact version.
• Force Address Sanitizer to not symbolize during fuzzing campaigns. Symbolizing is only useful to a human upon triaging ASAN crashes asynchronously of the fuzzing loop

[andreafioraldi]

@eqv wdyt?

[andreafioraldi]

I'd merge it if you agree

[rchildre3]

Ready for re-review