Merge branch 'release'

Increase patchlevel to 3.16.4

Merge branch 'knepley/feature-plex-explicit-timestepping' into 'main'

DM+TS: Add support for mass matrices

See merge request petsc/petsc!4683

Fix name of DMPlexTSComputeRHSFunctionFEM()

Plex+DS: Added support for explicit timestepping

DM+TS: Add support for mass matrices
- Added a lumped mass matrix for explicit timestepping
- Add functions for DMTS to manage the mass matrix
- Fix Plex mass matrix creation

MatSetPreallocationCOOLocal: convenience interface for COO assembly

MATAIJKOKKOS: support MatSetValuesCOO

SF: add PetscSFFetchAndOpWithMemTypeBegin()

Mat: add MatMultHermitianTranspose[Add]Equal()

Merge remote-tracking branch 'origin/release'

Merge branch 'barry/2022-01-14/improve-makefile-docs/release' into 'release'

Vastely improve documentation for using make and cmake with PETSc applications

See merge request petsc/petsc!4719

Merge remote-tracking branch 'origin/release'

Add TSRemoveTrajectory()

Update doc/petsc.bib

Merge branch 'stefanozampini/hypre-cuda-64idx' into 'main'

Enable HYPRE GPU with 64bit indices builds

See merge request petsc/petsc!4741

add petscmacros.h and move many macros over into it

Merge branch 'heeho/feature-newtontrdc' into 'main'

Newton Trust Region Dogleg Cauchy nonlinear solver

See merge request petsc/petsc!4294

configure: HYPRE + CUDA and 64bit indices only works in mixedint configuration

Merge branch 'barry/2022-01-02/minor-sellmat' into 'main'

MatSELL maintenance and documentation

See merge request petsc/petsc!4715

snes: Add new type SNESNEWTONTRDC for Newton Trust Region Dogleg Cauchy

Improve discussion of the use of PETSc with make and cmake

Commit-type: documentation
\spend 5h

After making docs print to screen how to view the docs

Commit-type: documentation
\spend 1m

Slightly improve the manual pages for MATSELL

Commit-type: documentation
\spend 45m

DMPlexLabelsLoad_Internal works in parallel.

DMPlexLabelsLoad: add PetscSF sfXC arg.