update amplitude runtime to support XCM reserve transfer for USDT

[b-yap]

Closes task #83

General overview of the changes:

Aside from the tasks mentioned in the ticket, this PR also includes:

• adding Statemine and its USDT in the xcm configuration of Amplitude.
• updating the test cases that will cater to both the pendulum and amplitude.
  • moving up the project from runtime/integration-tests/pendulum to runtime/integration-tests
  • moved ALL dependencies under [dev-dependencies] (see the updated Cargo.toml)
  • combined setup.rs and polkadot_test_net.rs into mock.rs
  • created a macro for the test cases: test_macros.rs
  • broke down tests.rs to 2: pendulum_tests.rs and amplitude_tests.rs

note: Statemint and Statemine have different issued balances, after performing XTokens::transfer() in Pendulum and Amplitude. See line 454 to 456 in test_macros.rs.

[ebma]

Thanks for adding my requested changes @b-yap.

While at first, it might seem like there is still some code that can be deduplicated, I think it's good the way it is right now. For example, some parameters like the IDs are shared between the Polkadot and Kusama asset hub, but still have separate definitions in runtime/common/src/lib.rs but I think it's better this way because we can't necessarily always assume that this is the case. There could have been differences since the Polkadot and Kusama AssetHub are different parachains after all.

LGTM

[ebma]

The previous CI already passed and we only added comments so I will merge it without waiting.