[x] I made sure to follow the project's coding style
[ ] I've updated the documentation with the relevant information (if needed)
Detailed description
The ThreadsWidget and ProcessesWidget column index enumerators having the same name with differing definitions violates the C++ One Definition Rule. These patches move those enums into the respective classes of each of these widgets, happily allowing differing definitions with the same name, and brings these two widgets into alignments with other widgets that define the column indexes similarly.
Test plan (required)
I've tested that the widgets touched here still function as expected.
Your checklist for this pull request
Detailed description
The ThreadsWidget and ProcessesWidget column index enumerators having the same name with differing definitions violates the C++ One Definition Rule. These patches move those enums into the respective classes of each of these widgets, happily allowing differing definitions with the same name, and brings these two widgets into alignments with other widgets that define the column indexes similarly.
Test plan (required)
I've tested that the widgets touched here still function as expected.
Closing issues
Closes #3316