* Set an explicit 2018 edition for Rust tests
* Replace all `std` usage with `core` and `alloc` in Rust code generator
* Update the generated files
* Make Rust tests actually use no_std when the corresponding feature is enabled
* Fix 64-bit default numeric enum values in typescript
If you had a default value that wasn't a valid enum value (e.g., a zero
if you used a bit_flag setting, like you get with AdvancedFeatures
in reflection.fbs), we weren't using BigInt.
* Run generate_code.py
* [DART] Handle deprecated fields & invalid enum defaults
* Update .NET test
