--exception:goto switch for deterministic exception handling (#12977)

This implements "deterministic" exception handling for Nim based on goto instead of setjmp. This means raising an exception is much cheaper than in C++'s table based implementations. Supports hard realtime systems. Default for --gc:arc and the C target because it's generally a good idea and arc is all about deterministic behavior.

Note: This implies that fatal runtime traps are not catchable anymore! This needs to be documented.

doc/advopt.txt

@@ -98,12 +98,13 @@ Advanced options:
   --skipProjCfg:on|off      do not read the project's configuration file
   --gc:refc|markAndSweep|boehm|go|none|regions
                             select the GC to use; default is 'refc'
+  --exceptions:setjmp|cpp|goto|quirky
+                            select the exception handling implementation
   --index:on|off            turn index file generation on|off
   --putenv:key=value        set an environment variable
   --NimblePath:PATH         add a path for Nimble support
   --noNimblePath            deactivate the Nimble path
   --clearNimblePath         empty the list of Nimble package search paths
-  --noCppExceptions         use default exception handling with C++ backend
   --cppCompileToNamespace:namespace
                             use the provided namespace for the generated C++ code,
                             if no namespace is provided "Nim" will be used