Add xcm upm mock endpoint and tests #5051

Job	Run time
set-tags	7s
cargo-toml-feature-propagation	1m 54s
check-copyright	4s
cargo-clippy	2m 24s
Check with rustfmt	14s
toml-formatting	51s
build	2m 19s
typescript-formatting	18s
typescript-linting	16s
check-api-augment	1s
Check WASM runtimes with Twiggy	1s
rust-test	1s
typescript-dancebox-specs	1s
typescript-tests	1s
typescript-tests-flashbox	1s
typescript-tests-frontier	1s
typescript-tests-relay	1s
typescript-tests-simple-template	1s
zombienet-tests	1s
chopsticks-upgrade-test	1s
zombienet-test-upgrade	1s
zombienet-test-upgrade-containers	1s
zombienet-test-upgrade-starlight	1s
docker-tanssi	1s
	8m 42s

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