Several event-loop operations bounded their runtime with
tokio::time::timeout(budget, run_event_loop()) or a select! against a
timer. When the timer wins, tokio drops the run_event_loop future
mid-poll; deno_core enters the isolate while polling, so the drop leaves
the isolate entered on the OS thread. Under concurrent CDP work a second
page's execute_script then trips heap->isolate() == TryGetCurrent() and
aborts the process (#430).
Drive the loop with poll_event_loop inside a poll_fn instead. It creates
and drops its own isolate scope per call, so stopping between ticks never
leaves the isolate entered. Convert resolve_promises_until,
run_event_loop_bounded, resolve_promises, the mod_evaluate settle in
load_module and load_inline_module, and the two navigation settle loops
in page.rs. Add poll_event_loop_once as the cancellation-safe single-tick
primitive the settle loops use.
Keeps the obstacle course at 33/33. This is hardening toward #430; the
residual concurrency abort still needs the thread-per-runtime refactor
that v8_lock.rs calls the "Option 2" fix.
Refs #430.
sycatle
45df429d99