Add `Lock` to std

[armanbilge]

trafficstars

Spinning out of https://github.com/typelevel/cats-effect/pull/3480#discussion_r1125597170.

The API would look something like:

abstract class Lock[F[_]] {
  def shared: Resource[F, Unit]
  def exclusive: Resource[F, Unit]
}

[ChristopherDavenport]

https://github.com/davenverse/lock - Available as some prior art.

[djspiewak]

…with the caveat that we can only implement reentrancy for IO, not for general effect types, since reentrancy requires some form of fiber identity (which we can access using IOLocal).

[kevchuang]

Hi, I would like to help on this issue !