Enable Jit for Generators, Asyncs and Async Generators

[rhuanjl]

This PR enables the JIT in both FullJit and SimpleJit mode for Generator Functions, Async Functions and Async Generator Functions (Collectively referred to internally as Coroutines)

Exceptions

• excludes ARM - I don't have access to an ARM machine to test, and our CI doesn't have ARM so seemed reckless to enable
• excludes functions containing try/catch, may introduce complexities and not yet tested
• disabled when a debugger is attached - may introduce complexities and not yet tested

Work Done in this PR

1. Fix register mismatch in Jit

   • This was a bug in yield* statements within Async Generators
   • the Lifetime of registers used to store the iterator statement would be incorrect
   • fixed by using additional regs to extend the lifetime

2. Fix handling of For-In

   • For-in loops use an enumerator objector stored in a cache
   • the logic to restore this across yields was not working correctly
   • fix by simplifying/removing a couple of steps and moving the load nearer to the point it is used

3. Disable BailOnNoProfile in Coroutines

   • BailOnNoProfile results in code after it being marked as Dead
   • Consider the below example:
   • if a BailOnNoProfile is inserted after the yield the ++i is marked as dead
   • as ++i is dead, i is marked as a single definition int - a constant
   • then you get yield 0 -> BailOnNoProfile -> yield 1 (in the interpreter) -> try jitted code again - Bails out with i = 0 as it is a const -> yield 1 (in the interpreter)

for (let i = 0; i < 3; ++i)
{
  yield i;
} 

4. Remove unnecessary startup yield

   • this is a minor optimisation BUT in the context of jitted generators avoids a compulsory extra bailout
   • also makes code much neater

5. Enable

   • change flags so it's all enabled
   • add test cases for key bugs mentioned above

Future Work
A. Look at enabling for functions containing try/catch - needs to be explored don't know what issues may arise
B. Create an alternative form of BailOnNoProfile that can be used in Coroutines
C. Look at Jitting loop bodies that don't contain yield - (including loop bodies in Modules)

Fix #5877

[rhuanjl]

@ppenzin sorry I know this isn't our top priority but I've been wanting to get it in for so long.... Please could you take a look when you have time.

[ppenzin]

I am glad you got it fixed, agree we should check this while it is still fresh. Do you want this shipping as part of the upcoming release? If not, we can cut the release branch right before merging it in.

[ppenzin]

Looks good.