Zeroize seed

[AaronFeickert]

Description

This PR ensures that seeds are zeroized after they are constructed from mnemonics.

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature/Enhancement (non-breaking change which adds functionality or enhances an existing one)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation update
• [ ] Refactor
• [ ] New or updated tests

Checklist

• [x] I have performed a self-review of my code.
• [x] I have commented my code where necessary.
• [x] I have updated the documentation if needed.
• [x] My changes do not introduce new warnings.
• [ ] I have added tests that prove my changes are effective or that my feature works.
• [x] New and existing tests pass with my changes.

Related Issues

Partially addresses Jira ticket 497.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 64.28571% with 5 lines in your changes missing coverage. Please review.

Project coverage is 57.27%. Comparing base (ed4013c) to head (585393c). Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
bin/strata-cli/src/seed.rs	64.28%	5 Missing :warning:

@@            Coverage Diff             @@
##             main     #412      +/-   ##
==========================================
+ Coverage   57.18%   57.27%   +0.08%     
==========================================
  Files         257      257              
  Lines       27144    27147       +3     
==========================================
+ Hits        15523    15549      +26     
+ Misses      11621    11598      -23     

Files with missing lines	Coverage Δ
bin/strata-cli/src/seed.rs	53.02% <64.28%> (+0.66%)	:arrow_up:

... and 6 files with indirect coverage changes