Allow operation for optional try

[xwu (Xiaodi Wu)]

SE-0217 - The "Unwrap or Die" operator

Proposal rejected The core team has decided to reject this proposal as written. However, the core team concurs that the motivating problems posed by the proposal are important to solve, as did an overwhelming majority of commenters who participated in the public review. The fact that the only fixit the compiler offers to unwrap an Optional is to use the ! operator is an unfortunate legacy of the Swift 1.0 days, before anything in the SDKs Swift was designed to work with had been audited for nul…