tendermint: box headers in Misbehaviour message

[mina86]

Header type is quite large. Misbehaviour holds two of those. This becomes an issue on platforms with small stack—such as Solana—where keeping (even temporary) local variable may lead to stack overflow.

Fix that by Boxing each of the headers in the Misbehaviour message.

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PR author checklist:

• [x] Added changelog entry, using unclog.
• [x] Added tests.
• [x] Linked to GitHub issue.
• [x] 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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 64.06%. Comparing base (987ec42) to head (83d3d52).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1145 +/- ## ======================================= Coverage 64.06% 64.06% ======================================= Files 217 217 Lines 21049 21049 ======================================= Hits 13484 13484 Misses 7565 7565 ```

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