runners: bench: Renamed bench m -> probe

This needed a different name, and "bench probe" is sort of reminiscent
of the "debug probes" you can use to measure things in the real world.

Maybe this is just my embedded engineering background poking through,
but honestly anything is better than a single char m, especially for a
non-integer field.

scripts/bench.py

@@ -1092,7 +1092,7 @@ def run_stage(name, runner, bench_ids, stdout_, trace_, output_, **args):
                 '|' '(?P<path>[^:]+):(?P<lineno>\d+):(?P<op_>assert):'
                     ' *(?P<message>.*)'
                 '|' '(?P<op__>benched)'
-                    ' (?P<m>[^\s]+)'
+                    ' (?P<probe>[^\s]+)'
                     ' (?P<n>\d+)'
                     '(?:'
                         '(?:'
@@ -1185,7 +1185,7 @@ def run_stage(name, runner, bench_ids, stdout_, trace_, output_, **args):
                         if args.get('keep_going'):
                             proc.kill()
                     elif op == 'benched':
-                        m_ = m.group('m')
+                        probe_ = m.group('probe')
                         n_ = int(m.group('n'))
                         # parse measurements
                         def dat(v):
@@ -1214,7 +1214,7 @@ def run_stage(name, runner, bench_ids, stdout_, trace_, output_, **args):
                                     'suite': last_suite,
                                     'case': last_case,
                                     **last_defines,
-                                    'm': m_,
+                                    'probe': probe_,
                                     'n': n_,
                                     'bench_reads': reads_,
                                     'bench_progs': progs_,
@@ -1401,7 +1401,7 @@ def run(runner, bench_ids=[], **args):
         output = BenchOutput(args['output'],
                 ['suite', 'case'],
                 # defines go here
-                ['m', 'n',
+                ['probe', 'n',
                     'bench_reads',
                     'bench_progs',
                     'bench_erases',