Change METTS example to use product initial state and print product states

[emstoudenmire]

In response to this forum post, this PR changes the initial state for the METTS example code to be a product state, similar to the other initial states later in the algorithm to avoid potential confusion. It also adds printing of each sampled product state while the algorithm runs.

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.29%. Comparing base (c01cba6) to head (fb1f9c3).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #165   +/-   ##
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  Coverage   90.29%   90.29%           
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  Files          54       54           
  Lines        3605     3605           
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  Hits         3255     3255           
  Misses        350      350           

Flag	Coverage Δ
docs	18.00% <ø> (ø)

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