fix: packet sequence in Timeout handlers should be encoded in big-endian

[en]

Description

refer to:
// Note: We expect the return to be a u64 encoded in big-endian. Refer to ibc-go:
// https://github.com/cosmos/ibc-go/blob/25767f6bdb5bab2c2a116b41d92d753c93e18121/modules/core/04-channel/client/utils/utils.go#L191

The seq_on_a of MsgTimeout packet should be encoded as a big-endian bytes.
Here's a code snippet to show this problem.
https://gist.github.com/en/e4f6befdef94b1e906ed0054709ccd4b

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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

All modified and coverable lines are covered by tests ✅

Comparison is base (de2c530) 70.69% compared to head (d7e375d) 70.69%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1004   +/-   ##
=======================================
  Coverage   70.69%   70.69%           
=======================================
  Files         178      178           
  Lines       17919    17870   -49     
=======================================
- Hits        12667    12634   -33     
+ Misses       5252     5236   -16     

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[Farhad-Shabani]

Nice catch @en! Thanks for this complete report. 👌🏻

Let’s apply the following changes:

1. This should be fixed here as well for the MsgTimeoutOnClose.

2. Let’s revise this to_vec method with self.0.to_be_bytes.to_vec() implementation and update it’s docstring, so we can afterwards call it on the msg.packet.seq_on_a

3. Dress up the PR with a unclog.

Then we are all set!

[Farhad-Shabani]

🙏🏻