Merge branch 'tisaac/feature-log-handler' into 'main'

Deglobalize logging into PetscLogHandler and PetscLogState

See merge request petsc/petsc!6709

Profiling: Add composed functions for default log handler functions

This makes them extensible to other implementations.
Where appropriate, the global log handler will now dispatch
these functions t

Profiling: Add composed functions for default log handler functions

This makes them extensible to other implementations.
Where appropriate, the global log handler will now dispatch
these functions to all running log handlers.

It is not always appropriate to dispatch to all running log handlers:
when a single return value is expected or when a filename
is given, it will continue to dispatch only to the default
log handler.

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Profiling: Add tutorial for implementing a PetscLogHandler

sys/tutorials/ex7.c implements all log handling callbacks using only the
public interface and also demonstrates what to expect in
PetscLogH

Profiling: Add tutorial for implementing a PetscLogHandler

sys/tutorials/ex7.c implements all log handling callbacks using only the
public interface and also demonstrates what to expect in
PetscLogHandlerStagePush() and PetscLogHandlerStagePop()
regarding the transition from old stage to new stage.

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