Alternative to https://github.com/denoland/deno/pull/18726.
This was suggested by @piscisaureus. It's a bit ugly, but it does the
work and makes cloning `JsRealm` very cheap, while not requiring
invasive changes.
Also managed to remove some vector and `v8::Global` clones which yields
about 5% improvement in the "async_ops_deferred.js" benchmark.
This PR:
```
time 1689 ms rate 592066
time 1722 ms rate 580720
time 1629 ms rate 613873
time 1578 ms rate 633713
time 1585 ms rate 630914
time 1574 ms rate 635324
```
`main` branch:
```
time 1687 ms rate 592768
time 1676 ms rate 596658
time 1651 ms rate 605693
time 1652 ms rate 605326
time 1638 ms rate 610500
```
This commit refactors "deno_core" to do fewer boundary crossings
from Rust to V8. In other words we are now calling V8 from Rust fewer
times.
This is done by merging 3 distinct callbacks into a single one. Instead
of having "op resolve" callback, "next tick" callback and "macrotask
queue" callback, we now have only "Deno.core.eventLoopTick" callback,
which is responsible for doing the same actions previous 3 callbacks.
On each of the event loop we were doing at least 2 boundary crosses
(timers macrotask queue callback and unhandled promise rejection
callback) and up to 4 crosses if there were op response and next tick
callbacks coming from Node.js compatibility layer. Now this is all done
in a single callback.
Closes https://github.com/denoland/deno/issues/18620
