Trie leaf iterate

[asdacap]

• Add ability to iterate trie leaf.
• Important for snap sync.
• Make it easier to make range proof tests.
• Uses a consumer func, as the stop condition can be complicated.
  • I guess you can convert it to iter.Seq2[KV, err] if you want.
• Can be optimized, but unlikely to make much of a difference.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 76.47059% with 8 lines in your changes missing coverage. Please review.

Project coverage is 75.39%. Comparing base (4e6dcd7) to head (b614c2e). Report is 107 commits behind head on main.

Files	Patch %	Lines
core/trie/trie.go	71.42%	3 Missing and 3 partials :warning:
core/trie/key.go	84.61%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1907 +/- ## ========================================== - Coverage 75.43% 75.39% -0.05% ========================================== Files 97 97 Lines 8342 8376 +34 ========================================== + Hits 6293 6315 +22 - Misses 1519 1526 +7 - Partials 530 535 +5 ```

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[pnowosie]

Closing. This is already part of #2035 and then we will continue from that one.