feat(worstcase): add report_individual flag for per-record member_prob

[shamykyzer]

closes #452

adds a report_individual flag to WorstCaseAttack (default False)

when set to True, each repetition's metrics dict gets an "individual" key holding per record member_prob and member, matching how LIRAAttack and QMIAAttack already report per record results

this lets MetaAttack fold worstcase into its vulnerability matrix later, that wiring is a separate follow up

[rpreen]

This still needs clean up? There are conflicts to be resolved; the PR title scopes it to "worstcase" yet introduces a variety of changes to tests for other attacks, the introduction of a constants module, a meta attack example, and changes to the readme, etc. The initial comment indicates that this PR is stacked on top of #441, but that appears to now be merged, so why are there still so many changes unrelated from the description?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.65%. Comparing base (85c9f0f) to head (5b62d2e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #461   +/-   ##
=======================================
  Coverage   99.65%   99.65%           
=======================================
  Files          27       27           
  Lines        3436     3439    +3     
=======================================
+ Hits         3424     3427    +3     
  Misses         12       12           

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