fix(lib/trie): deep copy subvalue byte slices to allow GC

[qdm12]

Changes

Some subvalues passed to or returned from trie methods are sometimes held in external data structures from the callers, preventing the GC from removing them when the root node is removed.

This simply deep copies subvalues instead of returning/passing them directly to in memory trie nodes.

Tests

go test -tags integration github.com/ChainSafe/gossamer

Issues

#1936

Primary Reviewer

@timwu20

[codecov]

Codecov Report

Merging #2913 (71eb78f) into development (0a8ac42) will decrease coverage by 0.17%.
The diff coverage is 100.00%.

❗ Current head 71eb78f differs from pull request most recent head 27309d0. Consider uploading reports for the commit 27309d0 to get more accurate results

Additional details and impacted files

@@               Coverage Diff               @@
##           development    #2913      +/-   ##
===============================================
- Coverage        63.23%   63.05%   -0.18%     
===============================================
  Files              219      219              
  Lines            27563    27571       +8     
===============================================
- Hits             17429    17386      -43     
- Misses            8520     8572      +52     
+ Partials          1614     1613       -1     

[qdm12]

Closing this, it doesn't really make sense. The GC should be able to remove a trie node even though one of its field references a byte slice used somewhere else.