Add integration test for bridge transfer (assets, ping, ...) based on xcm-emulator

[bkontur]

xcm-emulator is comming soon to the Cumulus,
and it has capabilities to test isolated runtimes without running zombienet or local network, it has kind of custom/hacked transport layer for UMP/DMP.

So with this feature we can easily use statemine / bridge-hub-kusama/ bridge-hub-polkadot/ westmint|statemint runtimes in one rust test to send/receive XCM messages and see if it is working.

Need to find out, which one is final xcm-emulator, because now there are several PRs and this is progress, so we need to wait a little bit:
paritytech/cumulus#2502
paritytech/cumulus#2447
paritytech/cumulus#2480

[NachoPal]

@bkontur this is the one paritytech/cumulus#2447 that will be initially merged.

After that I'll open a new one, but that one will probably not have yet the capability to work for bridges.

After that one I'll work on enabling the mock bridges transport layer..

[EmmanuellNorbertTulbure]

Now possible with monorepo

[bkontur]

closing, we have emulated tests for asset transfer Rococo/Westend in polkadot-sdk,
and we just need to add them to the fellows repo: #2791