Edit-and-continue needs to be disabled for foreach loops that contain out vars

[gafter]

See also #1503, #12688
/cc @tmat @jaredpar

Because out vars and patterns can introduce variables in the expression of a foreach loop, but the declaration of the foreach loop is not represented as a node, the current approach to edit-and-continue will break if a foreach loop contains either out variables or pattern-matching in the expression. We will either need to disable edit-and-continue somehow, or begin parsing the foreach loop into a new node form that contains a syntax node for the variable declaration. The latter is proposed in #12688.

/cc @CyrusNajmabadi @jcouv @VSadov

[AdamSpeight2008]

Or make it an error in those cases.

[jcouv]

With PR #13754, edits are disallowed in an active method that has any out var.