Add on_initialize and on_finalize hooks to xcm-emulator

[NachoPal]

It was found here: #2703 that on_initialize and on_finalize hooks were not triggered in xcm-emulator.

on_initialize and on_finalize attributes should be added to decl_test_parachains and decl_test_relay_chains macros expected struct arguments (similar to on_init) attribute. There, can be optionally added those pallets on_initialize and on_finalize hooks strictly needed for the tests.