Add Import Attributes proposal

* Add Import Attributes proposal
* `npm run format`
* Updates from review
* Changes from review
* Do not re-define ImportDeclaration
* Add `assert` deprecated syntax to `export ... from`
* Remove `[no LineTerminator here]` before `with`
* Use optional symbols to reduce grammar
* Update ImportEntries and ExportEntry to use ModuleRequest Records
* Review from Michael
* Replace AttributeKey with LiteralPropertyName
* Separate ModuleRequest and LoadedModuleRequest fields
* Validate attrs when lodaing deps and not when parsing
* Merge `AssertClause` into `WithClause`, and fix missing SDOs
* Fix type annotation
* Simplify AttributesKeyword
* Reviews
* Review
* Remove support for float and bigint literal keys
* Update wording

Author: nicolo-ribaudo