BENCH: profile memleaks asv

* add some `asv` peak memory benchmarks as regression guards
against gh-811; the only thing missing (IMO) here to completely
close gh-817 is a version of the log file with `HEATMAP` in it (see
the diff comments for why I don't have this for `asv` suite at the moment)

* although this won't automatically run in CI because it takes
too long and too much memory, it still seems to do an excellent
job of being sensitive to the patched leaks over the recent
history of our project:

- `asv continuous -e -b "peakmem.*" b6c8599 main`

```
       before           after         ratio
     [b6c8599]       [3fb2c36]
     <treddy_memleak_cffi_only_pt2~1>       <main>
-            239M              76M     0.32  cffi_backend.RetrieveLogData.peakmem_log_get_record('LUSTRE')
-            241M              76M     0.32  cffi_backend.RetrieveLogData.peakmem_log_get_record('H5F')
-            257M            75.8M     0.30  cffi_backend.RetrieveLogData.peakmem_log_get_record('STDIO')
-            289M              76M     0.26  cffi_backend.RetrieveLogData.peakmem_log_get_record('MPI-IO')
-            303M              76M     0.25  cffi_backend.RetrieveLogData.peakmem_log_get_record('POSIX')
-            304M            75.4M     0.25  cffi_backend.RetrieveLogData.peakmem_log_get_record('DXT_POSIX')
-            304M            75.3M     0.25  cffi_backend.RetrieveLogData.peakmem_log_get_record('DXT_MPIIO')
-            324M            75.8M     0.23  cffi_backend.RetrieveLogData.peakmem_log_get_record('H5D')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('DXT_POSIX')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('H5F')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('H5D')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('STDIO')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('MPI-IO')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('DXT_MPIIO')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('LUSTRE')
-           23.7G            75.4M     0.00  cffi_backend.RetrieveLogData.peakmem_log_get_mounts('POSIX')

SOME BENCHMARKS HAVE CHANGED SIGNIFICANTLY.
PERFORMANCE INCREASED.
```

Author: tylerjereddy

darshan-util/pydarshan/benchmarks/benchmarks/cffi_backend.py

@@ -0,0 +1,33 @@
+from darshan.backend import cffi_backend
+from darshan.log_utils import get_log_path
+
+
+class RetrieveLogData:
+    # see gh-811
+
+    # TODO: maybe produce a version of the log that also
+    # has runtime HEATMAP to guard memory leaks on that module;
+    # part of the issue here is
+    # perhaps the following to pull in new log repo files:
+    # https://github.com/darshan-hpc/darshan-logs/issues/15
+
+    params = ['POSIX', 'MPI-IO', 'H5F', 'H5D', 'LUSTRE', 'STDIO', 'DXT_POSIX', 'DXT_MPIIO']
+    param_names = ["module"]
+
+
+    def setup(self, module):
+        self.ior_log_path = get_log_path("ior_hdf5_example.darshan")
+
+
+    def peakmem_log_get_record(self, module):
+        for i in range(100000):
+            log = cffi_backend.log_open(self.ior_log_path)
+            rec = cffi_backend.log_get_record(log, module)
+            cffi_backend.log_close(log)
+
+
+    def peakmem_log_get_mounts(self, module):
+        for i in range(100000):
+            log = cffi_backend.log_open(self.ior_log_path)
+            rec = cffi_backend.log_get_mounts(log)
+            cffi_backend.log_close(log)