[SwiftBindings] Revert emitting Swift projection on error

[jkurdek]

When generating projections we might encounter multiple scenarios in which we are not able to generate a correct projection. This can stem from a bug or scope limitation of supported scenarios. If we cannot generate correct code for the projection we should revert projecting all the related bits.

[jkurdek]

We could do this by creating something like "transactions" - when we're about to start projecting a method, we "start a transaction" which will reset all output buffers. Then we project/write and everything goes into output buffers, only when we're successfully done, we "commit" and appends the buffers to the actual output.
This would be more robust than trying to check for every error condition upfront - it's easy to miss something, and that doesn't count actual unexpected exceptions during the writing process (our bugs and so on). It would be really nice if the tool was resilient to its own bugs to some degree.

Originally posted by @vitek-karas in #2870 (comment)