fix: revert frozen_height to 0 for active clients in conversions

[Farhad-Shabani]

Description

In #1061, when converting an active Tendermint ClientState to its corresponding proto type, we set the frozen_height as None to ensure consistency when switching between domain and proto types. However, basecoin-rs revealed that the ibc-go driven chain can only properly decode the Protobuf encoded of an active ClientState value when the frozen_height is explicitly set to zero!

Integration test: informalsystems/basecoin-rs#151

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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/).
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Reviewer checklist:

• Reviewed Files changed in the GitHub PR explorer.
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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (06725c1) 67.06% compared to head (57dec21) 67.07%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1064      +/-   ##
==========================================
+ Coverage   67.06%   67.07%   +0.01%     
==========================================
  Files         204      204              
  Lines       20532    20543      +11     
==========================================
+ Hits        13769    13780      +11     
  Misses       6763     6763              

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[rnbguy]

Am I correct to conclude that frozen_height doesn't need to be Option<Height>? We can just use Height - as it is never set toNone.

[rnbguy]

I got my answer!

1. RawClientState never has None for frozen_client (ibc-go convention). The active case is denoted by RawHeight { number: 0, height: 0 }.
2. It's best to use Option<Height> and None will denote RawHeight { number: 0, height: 0 } which is invalid in our domain type Height.

[rnbguy]

One suggestion - otherwise, LGTM ✨