PoS claim rewards - add token transfer event (backport #4283)

[mergify]

Describe your changes

Emit a token transfer emit with "pos-claim-rewards" descriptor when claiming non-zero staking rewards.

An update to a live chain with this change can be applied via a gov proposal replacing the tx_claim_rewards wasm

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

---

This is an automatic backport of pull request #4283 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.18%. Comparing base (0979728) to head (cf6fba1).
Report is 4 commits behind head on maint-libs-0.47.

Additional details and impacted files

@@                 Coverage Diff                 @@
##           maint-libs-0.47    #4338      +/-   ##
===================================================
+ Coverage            74.17%   74.18%   +0.01%     
===================================================
  Files                  345      345              
  Lines               110624   110633       +9     
===================================================
+ Hits                 82058    82078      +20     
+ Misses               28566    28555      -11     

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