Improve runtime tests

[yrong]

The added unit test focus on the flow of submit inbound message(including proof verification logic) and check MessageReceived event with specified xcm_hash as expected.

Together with the previous emulated test then we have a basic ensurance that inbound flow always work as expected without runing e2e smoke test which is a bit too slow.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (150a785) 81.27% compared to head (3bfb3ec) 81.18%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1013      +/-   ##
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- Coverage   81.27%   81.18%   -0.09%     
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  Files          54       54              
  Lines        2238     2238              
  Branches       71       71              
==========================================
- Hits         1819     1817       -2     
- Misses        402      404       +2     
  Partials       17       17              

Flag	Coverage Δ
rust	81.33% <100.00%> (-0.11%)	⬇️

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[vgeddes]

I like the goals of the PR, however, I think the implementation introduces a big problem - tight coupling between the runtime benchmark code and the runtime test code. In other words, the modularity & composability of the codebase has been compromised.

The main symptom is that the runtime tests now depend on the runtime-benchmarks feature, which is not good.

This problem can be solved by some of the following approaches:

1. Adding a runtime-tests feature to the inbound-queue crate
2. Move the fixture data to pallets/inbound-queue/src/fixtures.rs, and conditionally declare it as a module using #[cfg(any(feature = "runtime-tests", feature = "runtime-benchmarks))]
3. Conditionally compile Config::Helper also using #[cfg(any(feature = "runtime-tests", feature = "runtime-benchmarks))]