WIP - delay locals capture from Vertx to contexts

[jponge]

I am wondering if we'd benefit from shifting the context local captures from the Vertx instance to the actual contexts creation. This involves a few allocations on duplication, but I don't think it'd be that much of a problem.

One possible improvement (but I have not verified) is that it could allow new ContextLocal instances to be registered after a Vertx context has been initialized.

WDYT?

[vietj]

what is the goal ?

[jponge]

One possible improvement (but I have not verified) is that it could allow new ContextLocal instances to be registered after a Vertx context has been initialized.

[jponge]

It's not necessarily meant to be merged, I'm really wondering if we need to set in stone the locals array this early in the lifetime. I've had a test in the IDE + debugger where running would fail because the ContextLocal arrived later so the array index was wrong.

[vietj]

the main reason the context local list is captured when creating a vertx instance, is that context are created assuming the list does not change and therefore there is an exact mapping of ContextBase#locals and VertxImpl#contextLocals.

If contextLocals changes, then a context created before the list is updated will have an incorrect local storage.