* In order to prevent ArrayBuffers from getting garbage collected by V8,
  we used to store a v8::Persistent<ArrayBuffer> in a map. This patch
  introduces a custom ArrayBuffer allocator which doesn't use Persistent
  handles, but instead stores a pointer to the actual ArrayBuffer data
  alongside with a reference count. Since creating Persistent handles
  has quite a bit of overhead, this change significantly increases
  performance. Various HTTP server benchmarks report about 5-10% more
  requests per second than before.

* Previously the Persistent handle that prevented garbage collection had
  to be released manually, and this wasn't always done, which was
  causing memory leaks. This has been resolved by introducing a new
  `PinnedBuf` type in both Rust and C++ that automatically re-enables
  garbage collection when it goes out of scope.

* Zero-copy buffers are now correctly wrapped in an Option if there is a
  possibility that they're not present. This clears up a correctness
  issue where we were creating zero-length slices from a null pointer,
  which is against the rules.

Use `--config`

Crashes while running wrk against
js/deps/https/deno.land/std/http/http_bench.ts

This reverts commit 972ac038.

Op dispatch is now dynamically dispatched, so slightly less efficient.
The immeasurable perf hit is a reasonable trade for the API simplicity
that is gained here.

Fixes #2169 

Co-authored-by: NBartek Iwańczuk <biwanczuk@gmail.com>
Co-authored-by: NLE GOFF Vincent <g_n_s@hotmail.fr>