Use secure RNG

[AaronFeickert]

Description

This PR updates an Rng trait bound to require a cryptographically-secure generator.

Type of Change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] 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

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

None.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 57.33%. Comparing base (2486f5c) to head (dfc58e0). Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
bin/datatool/src/main.rs	0.00%	3 Missing :warning:

@@            Coverage Diff             @@
##             main     #386      +/-   ##
==========================================
- Coverage   57.35%   57.33%   -0.02%     
==========================================
  Files         255      255              
  Lines       26953    26954       +1     
==========================================
- Hits        15459    15455       -4     
- Misses      11494    11499       +5     

Files with missing lines	Coverage Δ
bin/datatool/src/main.rs	0.00% <0.00%> (ø)

... and 5 files with indirect coverage changes