TrappistDropAssets XCM primitive (#109)

* bootstrap TrappistDropAssets

* split xcm-simulator

* enable TrappistDropAssets on runtime

* change test command on README

* test_xcm_trap

* add integration-tests

* todo weight

* fmt

* tests_misc

* lint test modules

* refactor: organise tests into module to maximise code re-use (#111)

* enable system events tracing

* fix asset trap integration-test events

* Format integration test (#112)

* test: fix test formatting

* test: remove unused variables

* comment out AssetsClaimed event assertion

* refactor: move variables closer to usage (#115)

Also removes unnecessary path prefixes

* test: fix borrow of moved values

* lint integration tests

* lint integration tests

* add comments to fn drop_assets

* test: format integration test (#116)

Co-authored-by: Frank Bell <[email protected]>
Co-authored-by: Frank Bell <[email protected]>