Remove JumpException, Next, Redo, etc. exceptions from old runtime

[subbuss]

These exceptions should no longer be thrown in the IR-based runtime. Consequently, all the try-catch handleres for these exceptions can be stripped out.

Audit these uses, verify that no runtime code throws these anymore, and see if any of these sites require equivalent IRReturnJump / IRBreakJump protection (unlikely, but doesn't hurt to verify while stripping out the old runtime ones).

[enebo]

We still have SPECIAL_JUMP which is used for all sorts of enumerable messages and so SpecialJump for a simple marker flow control exception instance is overkill so we should consider killing SpecialJumpException altogether for:

Exception SPECIAL_JUMP = new Exception();

There is a tiny risk some native exceptions use Return/Next/Redo but since they are never thrown in 9 I think it is correct for the extensions to error out and know about it sooner than later...

[chrisseaton]

How does IR represent control flow now, if not by exceptions? Especially NextException with blocks - that is handled by the yield-site, not by the block itself, is it? So it could be compiled separately from the yield-site and the control flow is non-local.

[subbuss]

IR uses exceptions as well. These older AST-runtime exceptions weren't being used. As for next, a next in a closure becomes a non-local return (which is handled using non-local exceptions anyway). https://github.com/jruby/jruby/blob/master/core/src/main/java/org/jruby/ir/IRBuilder.java#L2781-L2786

[subbuss]

Uh .. I am clearly rusty at this point, but, no, that is not a non-local return, just a simple return which transfers control back to the yielder, and so no exceptions involved in next handling.