SE-0483: `InlineArray` Literal Syntax

[Slava_Pestov]

@theundergroundsorcerer

there is a possibility that שnon negligible amount of valid and idiomatic existing code that uses arrays might suddenly stop compiling because of error: the compiler is unable to type-check this expression in reasonable time.

Adding a new type that conforms to a literal protocol doesn’t automatically introduce new overloads in existing expressions that don’t involve that type, see Replacing the Type Checker - #67 by Slava_Pestov.

Also this proposal isn’t about array literal syntax - that was covered in the original InlineArray proposal.

There is a bit of an unsolved language design issue with this though because InlineArray can’t conform to ExpressibleByArrayLiteral, so right now the literal syntax is hacked in. Ideally the protocol will be generalized but that won’t change what I wrote above.