ASMStar: enable patch coloring

[pbrubeck]

Description

Enables ASMStarPC and ASMVankaPC to group patches by color (non-overlapping vertex/Vanka-stars) into a block diagonal matrix. Coloring is enabled through the petsc option -pc_star_coloring.

As a benchmark consider the Poison equation on a 256x256 mesh solved with one process:

Solver     | Degree | Iterations | Time     
-----------------------------------------
ColorASM   |      3 |          7 | 4.3655
PCPatch    |      3 |          7 | 13.104
TinyASM    |      3 |          7 | 7.9988
PetscASM   |      3 |          7 | 76.184

Here all solvers are mathematically equivalent, and all of them except TinyASM use Cholmod for the Cholesky factorization of the patch matrices.

Depends on https://gitlab.com/petsc/petsc/-/merge_requests/9069

[rckirby]

This is a great idea -- it looks like user just adds a new option to the dictionary if we want to turn it on?

Probably we should have some minimal simple tests, such as parameterizing existing tests of ASMStarPC and ASMVankaPC to turn the coloring option off and on?