[xcm-emulator] Add on_initialize and on_finalize hooks

[0xmovses]

Closes #1384

[juangirini]

I appreciate the code formatting, but it is unrelated on some files. I would keep that in a separate PR

[NachoPal]

The PR is still very green. It is not even compiling, check the CI. Ping me again when you think it is done :)

[NachoPal]

I see you are only calling the hooks for Parachains. It should be called for Relay Chain also.

Can you prove it really works and the hooks calls are placed in the proper place? You could for example try to move AuraExt::on_initialize(1) from on_init to a new struct for hooks

[muharem]

Don't we want to have a similar to pallets above way to set the hooks?
In most cases we do not need a custom with OnHooks trait, but we just want to list for which pallets it should run on_initialize and on_finalize.
What you think? @0xmovses @NachoPal

[NachoPal]

I am not sure that something like:

  hooks = {
	  $($pallet_name:ident: $pallet_path:path,)*
  }

could be possible to be passed as argument of __impl_test_ext_for_parachain/relay()

Having the OnHooks trait also gives more flexibility to the dev in case he wants to execute some custom code during on_initialize/on_finalize()