swift234

[Parse/Sema][SR-1672] Improve diagnostics for trailing closures in stmt-condition (#3184)

Fix-it suggests normal argument expression, instead of of enclosing whole
expression with parens.

* Moved diagnostic logic to Sema, because we have to add correct argument
  label for the closure.

    if arr.starts(with: IDs) { $0.id == $2 } { ... }
                           ~~^
                           , isEquivalent:  )

* We now accept trailing closures for each expressions and right before `where`
  clause, as well as closures right before the body.

    if let _ = maybeInt { 1 }, someOtherCondition { ... }
                       ~^
                       (     )

    for let x in arr.map { $0 * 4 } where x != 0 { ... }
                        ~^
                        (          )