Specreduce version 1.9.0

[hpparvi]

This PR updates the changelog and the specreduce roadmap and prepares specreduce for the v1.9 release.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.72%. Comparing base (c6ce64a) to head (3d20227).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #306   +/-   ##
=======================================
  Coverage   91.72%   91.72%           
=======================================
  Files          18       18           
  Lines        2139     2139           
=======================================
  Hits         1962     1962           
  Misses        177      177           

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[tepickering]

let's go! thanks for all the work you've put into this release.

[hpparvi]

Thanks, @tepickering!