Rust Object API (#6070)

* inital commit of rust object api

* Required fields support.

* clang fallthrough

* Fix unused variables

* just don't fall through

* remove comment

* s/panic/unreachable

* Tests for object API

* Added defaults

* deleted unintentionally added files and updated .bat file

* fix bat file

* clang format

* Cargo clippy checks

* remove commented out code

* clippy allows

* Remove matches! macro since we're not yet at Rust v1.42

* install clippy in RustTest.sh

* move line

Co-authored-by: Casper Neo <cneo@google.com>

samples/sample_flexbuffers.rs

@@ -31,6 +31,7 @@ use flexbuffers::{BitWidth, Builder, Reader, ReaderError};
 //         {"damage": 15, "name": "great axe"},
 //         {"damage": 5, "name": "hammer"}]
 // }
+#[allow(clippy::float_cmp)]
 fn main() {
     // Create a new Flexbuffer builder.
     let mut builder = Builder::default();