Refactor connection handler unit tests to adapt with new API

[Farhad-Shabani]

Closes: #440

Remark

• Reusable components are kept inside the core::ics03_connection::handler. If we decide to apply such a writing test approach for the rest of the parts, it should be moved to a higher level inside core::handler
• The Option<ContextError> type for the Expect::Failure should be ContextError to know what error exactly we catch in a failure scenario. But here we aimed to fulfill the refactoring purpose and this (along with other tests) should be revised with the next improvement iteration

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PR author checklist:

• Added changelog entry, using unclog.
• Added tests.
• Linked to GitHub issue.
• Updated code comments and documentation (e.g., docs/).
• Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
• Manually tested (in case integration/unit/mock tests are absent).

[codecov]

Codecov Report

Base: 62.21% // Head: 61.14% // Decreases project coverage by -1.08% ⚠️

Coverage data is based on head (f4d373d) compared to base (0f3e03f).
Patch coverage: 93.53% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #441      +/-   ##
==========================================
- Coverage   62.21%   61.14%   -1.08%     
==========================================
  Files         131      131              
  Lines       17789    18105     +316     
==========================================
+ Hits        11068    11070       +2     
- Misses       6721     7035     +314     

Impacted Files	Coverage Δ
...s/ibc/src/clients/ics07_tendermint/client_state.rs	45.42% <0.00%> (-0.22%)	⬇️
crates/ibc/src/core/handler.rs	78.26% <ø> (ø)
...bc/src/core/ics04_channel/handler/chan_open_ack.rs	84.00% <ø> (ø)
...c/src/core/ics04_channel/handler/chan_open_init.rs	80.00% <ø> (ø)
crates/ibc/src/core/ics03_connection/handler.rs	46.66% <93.33%> (-40.00%)	⬇️
...core/ics03_connection/handler/conn_open_confirm.rs	70.76% <95.34%> (-8.34%)	⬇️
...src/core/ics03_connection/handler/conn_open_ack.rs	66.66% <95.94%> (-27.90%)	⬇️
...rc/core/ics03_connection/handler/conn_open_init.rs	65.58% <96.07%> (-31.51%)	⬇️
...src/core/ics03_connection/handler/conn_open_try.rs	65.81% <96.66%> (-30.14%)	⬇️
...bc/src/core/ics03_connection/msgs/conn_open_ack.rs	95.60% <100.00%> (+0.36%)	⬆️
... and 16 more

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[plafer]

Can we remove all changes in the ics04_channel module? This will cause a merge conflict with #430

[Farhad-Shabani]

There still would be conflict, because of the get_dummy_raw_msg_conn_open_*() changes and it does not take None anymore, How if we merge this PR after #430?

[plafer]

hmm, in that case let's just merge as is. We need to merge this first because the last step of #430 is to remove impl Readers/Keepers for MockContext, which needs this. They won't be big conflicts anyways

[plafer]

thank you for these high-quality tests! We can use them as a baseline when we implement #429