PetscInitialize() and PetscFinalize() wrapped:

- ierr = PetscInitialize();if (ierr) return ierr;
+ CHKERRQ(PetscInitialize());

- ierr = PetscFinalize();
- return ierr;
+ CHKERRQ(PetscFinalize());
+

PetscInitialize() and PetscFinalize() wrapped:

- ierr = PetscInitialize();if (ierr) return ierr;
+ CHKERRQ(PetscInitialize());

- ierr = PetscFinalize();
- return ierr;
+ CHKERRQ(PetscFinalize());
+ return 0;

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fixes from recent linter change

pluck ~1000 low hanging PetscCheckFalse() -> PetscCheck() fruit

rewrote the PetscLL macros as functions to let the linter understand them. Also helps
reduce the staggering amount of code duplication in Mat

chkerr and friends wrapped

Fix compilation warnings

-Wmissing-field-initializers -Wunused-but-set-variable