Make dataPtr private in Plugin class

[marcoag]

🦟 Bug fix

Summary

The dataPtr attribute on the Plugin Class is currently public. This PR makes it private. This is a quick fix as eventually classes should use GZ_UTILS_IMPL_PTR.

I also opened an issue here for future reference on the need of porting all remaining dataPtrs to use GZ_UTILS_IMPL_PTR.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #1268 (57678ee) into main (e98fcd8) will not change coverage.
The diff coverage is n/a.

❗ Current head 57678ee differs from pull request most recent head dd546a8. Consider uploading reports for the commit dd546a8 to get more accurate results

@@           Coverage Diff           @@
##             main    #1268   +/-   ##
=======================================
  Coverage   87.21%   87.21%           
=======================================
  Files         126      126           
  Lines       16304    16304           
=======================================
  Hits        14219    14219           
  Misses       2085     2085           

Impacted Files	Coverage Δ
include/sdf/Plugin.hh	93.75% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.