Commit only merkle tree

[Fraccaman]

Describe your changes

Adds a new leaf to the base merkle tree which can contain arbitrary data.

closes #2823

Indicate on which release or other PRs this topic is based on

Based on #2627

diff: https://github.com/anoma/namada/pull/2926/files/e138cfb7604744a45b8a84fc16a52ae86ec1c73f..35436191c8df9a1b18ef278d5de71e4f7287b203

Checklist before merging to draft

• I have added a changelog
• Git history is in acceptable state

[codecov]

Codecov Report

Attention: Patch coverage is 70.58824% with 230 lines in your changes are missing coverage. Please review.

Project coverage is 53.62%. Comparing base (2ba001d) to head (3543619).
Report is 135 commits behind head on main.

❗ Current head 3543619 differs from pull request most recent head 4a43fc9. Consider uploading reports for the commit 4a43fc9 to get more accurate results

Files	Patch %	Lines
crates/sdk/src/masp.rs	0.00%	95 Missing ⚠️
crates/merkle_tree/src/lib.rs	61.72%	31 Missing ⚠️
...s/apps/src/lib/node/ledger/shell/finalize_block.rs	87.83%	18 Missing ⚠️
crates/apps/src/lib/bench_utils.rs	0.00%	16 Missing ⚠️
crates/sdk/src/tx.rs	0.00%	14 Missing ⚠️
crates/state/src/wl_state.rs	74.00%	13 Missing ⚠️
...ates/apps/src/lib/node/ledger/shell/block_alloc.rs	89.47%	12 Missing ⚠️
crates/apps/src/lib/client/rpc.rs	0.00%	8 Missing ⚠️
.../apps/src/lib/node/ledger/shell/vote_extensions.rs	66.66%	6 Missing ⚠️
crates/gas/src/storage.rs	0.00%	6 Missing ⚠️
... and 9 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2926      +/-   ##
==========================================
- Coverage   53.88%   53.62%   -0.26%     
==========================================
  Files         308      308              
  Lines      100154    99425     -729     
==========================================
- Hits        53966    53318     -648     
+ Misses      46188    46107      -81     

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[tzemanovic]

added a fix from @yito88 (0950667)