Add Findzstd.cmake; change Windows find_packages usage to use it too

[daym]

• Add Findzstd.cmake

Description

This makes mamba find zstd when that zstd was built using their Makefile rather than their cmake (and hence their zstdConfig.cmake is not installed).

A logical cmake target zstd::libzstd_shared is created, referring to either a shared or a static library zstd (not specified which of static or shared to make it more general).

No zstdConfig.cmake in libzstd-dev in the following distributions:

• Ubuntu 20.04 LTS (libzstd-dev)
• Ubuntu 22.04 LTS (libzstd-dev)
• CentOS 8 / RHEL 8 (libzstd-devel)
• Debian 11 (Bullseye)
• Fedora 43
• Guix

A zstdConfig.cmake is in libzstd-dev in the following distributions:

• Arch Linux
• Debian 12 (Bookworm)

Type of Change

• Bugfix
• Feature / enhancement
• CI / Documentation
• Maintenance

Checklist

• My code follows the general style and conventions of the codebase, ensuring consistency
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I have run pre-commit run --all locally in the source folder and confirmed that there are no linter errors.
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.83%. Comparing base (59f22ac) to head (f59e665).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4159   +/-   ##
=======================================
  Coverage   50.83%   50.83%           
=======================================
  Files         237      237           
  Lines       28228    28228           
  Branches     2919     2919           
=======================================
  Hits        14351    14351           
  Misses      13874    13874           
  Partials        3        3           

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