Fix and Improve WASM CI

- Use latest Firefox
- Explicitly pin wasmtime and cargo-web
- Make sure our `wasm-bindgen-test-runner` and `wasm-bindgen` versions match

Run Rustfmt

* Simplify CI process for WASM

Run WASI tests, and run both stdweb/wasm-bindgen on both node and in browsers

These changes also remove the need for a separate tests/wasm_bindgen

* Use all pre-built binaries in the CI

* Fix Cargo.toml typo

Co-Authored-By: Artyom Pavlov <newpavlov@gmail.com>

* Fix install location

* Debug CI

Ensure and document that we do nothing when an empty slice is passed.

Note that this changes are for consistency, not to prevent UB.

* Fix Redox CI

* Bump libc version to fix Redox

This updates the documentation to explain exactly what we are doing on
this target. Also adds a test that the target builds without features.

The 'libc::syscall' function uses varargs - as a result, its arguments
are completely untyped. THe user must ensure that it is called with the
proper types for the targeted syscall - otherwise, the calling
convention might cause arguments to be put into the wrong registers.

This commit explicitly casts the arguments to 'libc::syscall' to the
proper type for the 'getrandom' syscall. This ensures that the correct
types for the target platform will always be used, instead of relying on
the types used happening to match those required by the target platform.