Fix memusage reporting

[rljacob]

Switch to 64-bit ints and /proc/status and fix build with HAVE_SLASHPROC

Memory usage values from /proc can exceed 2 GB, causing integer overflow with 32-bit int. Switch the C API to long
long and Fortran callers to integer(8).

Also switch from /proc/<pid>/statm (page counts) to /proc/<pid>/status (labeled KB fields) on Linux, reporting
VmHWM as "size" instead of VmSize to avoid inflation from GPU BAR mappings and other non-physical reservations.

Make sure HAVE_SLASHPROC is defined if available. The CMake build was missing -DHAVE_SLASHPROC, so the
GPTL code was falling through to the getrusage path which sets *size = -1 (an int -1)

Fixes #8425
[BFB]

[Copilot]

Pull request overview

Update GPTL-based memory reporting to avoid 32-bit overflows and to use more
meaningful Linux /proc metrics, then propagate the 64-bit API change through
Fortran callers and build configuration.

Changes:

• Switch GPTLget_memusage argument types from 32-bit int* to 64-bit
  long long*, and update affected Fortran callers to integer(8).
• On Linux, parse /proc/<pid>/status (VmHWM/VmRSS, etc.) instead of
  /proc/<pid>/statm, and print results in MB.
• Ensure HAVE_SLASHPROC is defined in the CMake build when appropriate.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
share/util/shr_mem_mod.F90	Update local memusage variables to 64-bit to prevent overflow and preserve MB conversions.
share/timing/GPTLprint_memusage.c	Update printing path to use long long memusage values and MB conversion.
share/timing/GPTLget_memusage.c	Change C API to long long* and switch Linux implementation to /proc/<pid>/status parsing.
share/timing/gptl.h	Update public prototype for GPTLget_memusage to long long* arguments.
share/timing/f_wrappers.c	Update Fortran-callable wrapper prototype/signature for 64-bit memusage arguments.
share/timing/CMakeLists.txt	Define HAVE_SLASHPROC in CMake builds when /proc support is detected.
components/homme/src/share/compose_test_mod.F90	Update Homme memusage locals to 64-bit for the new GPTL signature.
components/homme/src/preqx/share/prim_state_mod.F90	Update Homme memusage locals to 64-bit for the new GPTL signature.