This commit adds new compiler options -no-warning-as-error/-warning-as-error which allows users to specify behavior for exact warnings and warning groups.
The new message is:
"Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace."
1. In crash logs we used to print a message which points to the llvm bug tracking page. Now it points to the swift.org bug tracking guidelines.
2. Use the same message in all compiler diagnostics which ask the user to file a bug report.
rdar://problem/70488534
Let's replace use `llvm::sys::fs::RemoveFileOnSignal` with manual
tracking of created temporary files. Signals are unavailable on
Windows so all of the temporary files are going to be left in place
otherwise.
