Prune more Merkle tree snapshots

[yito88]

Describe your changes

The old Merkle tree snapshots for NoDiff and CommitData don't need to be saved.
The storage space was occupied by NoDiff Merkle tree snapshots.

This PR prunes the previous snapshots at every block commit.

• prune_merkle_tree_stores prunes subtree snapshots which are saved every block
  • Other snapshots which are saved every epoch are pruned as before
• read_merkle_tree_stores returns incomplete Merkle tree if the store type isn't specified i.e. if it is requested to restore all subtrees. (When the store type is specified, it returns an error if the store type snapshot doesn't exist.) get_merkle_tree will rebuild the incomplete subtrees.

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:

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 8 lines in your changes missing coverage. Please review.

Project coverage is 74.25%. Comparing base (47fc912) to head (ddecdfe).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/storage/src/mockdb.rs	63.63%	4 Missing ⚠️
crates/node/src/storage/mod.rs	92.30%	2 Missing ⚠️
crates/node/src/storage/rocksdb.rs	80.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4043   +/-   ##
=======================================
  Coverage   74.25%   74.25%           
=======================================
  Files         341      341           
  Lines      107271   107325   +54     
=======================================
+ Hits        79651    79694   +43     
- Misses      27620    27631   +11     

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[grarco]

lgtm, thank you!