* Upgrade all crates to the Rust 2021 edition
I've personally started using the new format strings for things like
`panic!("some message {foo}")` or similar and have been upgrading crates
on a case-by-case basis, but I think it probably makes more sense to go
ahead and blanket upgrade everything so 2021 features are always
available.
* Fix compile of the C API
* Fix a warning
* Fix another warning
* Move all examples to a top-level directory
This commit moves all API examples (Rust and C) to a top-level
`examples` directory. This is intended to make it more discoverable and
conventional as to where examples are located. Additionally all examples
are now available in both Rust and C to see how to execute the example
in the language you're familiar with. The intention is that as more
languages are supported we'd add more languages as examples here too.
Each example is also accompanied by either a `*.wat` file which is
parsed as input, or a Rust project in a `wasm` folder which is compiled
as input.
A simple driver crate was also added to `crates/misc` which executes all
the examples on CI, ensuring the C and Rust examples all execute
successfully.
