Different approach to returning schedulers

Fix resume from wrong scheduler

Add and update tests

More tests

Throw UnwindExit in unfinished fibers

Call schedulers on script end, but only if there is no fatal error

Add initial tests

Deleted outdated demos. Will add new ones using scripts added for tests.

Push scheduler shutdown after destructors and registered shutdown functions

Rarrange scheduler exception handling

Fix schedulers running on fatal error

Revert scheduler efree

I knew this wasn’t correct…

Remove now unnecessary fiber state

Fix scheduler memory leak

Not sure why efree appears necessary for schedulers but not other fibers… this may not be the correct approach.

Throw if scheduler fiber ends

Also better cleanup of fiber schedulers, before and after register_shutdown_function().

Move fiber cleanup

register_shutdown_function() may now use Fiber::await().

Split out fiber continuation variables

Reduces memory for scheduler fibers.

Update for PHP 8-RC1

Ignore UnwindExit

Clean up fibers after scheduler throw

Fatal error if scheduler throws an exception

Switch to dead fiber before destruction

Undefined destructor order has tripped me up in user code, why should extension code be any different.

Revert a dtor move

Move some zval_ptr_dtor

Throw if await called in Awaitable::onResolve()

Keep list of fibers for GC

Unfinished fibers were leaking prior to this change.