Merge branch 'barry/2023-11-06/doc-cleanup-man-page-processing' into 'main'

Move doc/classic materials to doc/manualpages

See merge request petsc/petsc!7000

Organize the Mat coloring, partitioning, coarsening, and ordering in a common directory

under the SUBMANSEC of MatGraphOperations instead of MatOrderings

Commit-type: housekeeping