benches: Added several benchmarks

Based on some experience out-of-tree:

- bench_rbyd        - Simple rbyd attr/id litmus benchmark
- bench_btree (new) - Simple btree id/name litmus benchmark
- bench_file (new)  - Simple file read/write litmus benchmark
- bench_dir (new)   - Simple dir read/write/stat litmus benchmark
- bench_wt          - Heavy-duty write-throughput benchmark
- bench_rt (new)    - Heavy-duty read-throughput benchmark

Benches take a long time to run for useful results, so we probably don't
want to go crazy with them like with the tests.

Honestly, we may want to chop this down to just the
write/read-throughput benches.

benches/bench_wt.toml

@@ -1,4 +1,5 @@
 # High-level write-throughput benchmarks
+after = ['bench_file', 'bench_dir']
 
 # these are common and can be overridden suite-wide
 #
@@ -9,10 +10,6 @@ defines.SIZE = '1024*1024' # 1 MiB
 defines.CHUNK = 64
 defines.SEED = 42
 
-# note FILE_SIZE is bench_*_many specific
-defines.FILE_SIZE = 'CHUNK'
-defines.FILE_COUNT = '(SIZE+(FILE_SIZE-1)) / lfs3_max(FILE_SIZE, 1)'
-
 # simulated time, in nanoseconds, to run the bench
 defines.SIM_TIME = '60ULL*60ULL*1000ULL*1000ULL*1000ULL' # 1 hour
 # simulation size in bytes
@@ -21,15 +18,12 @@ defines.SIM_SIZE = 0
 # set this to true to skip bench warmup
 defines.SKIP_WARMUP = false
 
-# don't fruncate, this is logging specific
-defines.NO_FRUNCATE = 0
-
-
 # include common bench helpers
 code = '''
-#include "benches/bench_helpers.h"
+    #include "benches/bench_helpers.h"
 '''
 
+
 # sequential write throughput
 [cases.bench_wt_seq]
 code = '''
@@ -164,6 +158,7 @@ code = '''
 # 1. fruncate/rotations instead of rewind+truncate
 # 2. sync called on every write
 [cases.bench_wt_logging]
+defines.NO_FRUNCATE = false
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;
@@ -239,6 +234,8 @@ code = '''
 
 # many small file write throughput
 [cases.bench_wt_many]
+defines.FILE_SIZE = 'CHUNK'
+defines.FILE_COUNT = '(SIZE+(FILE_SIZE-1)) / lfs3_max(FILE_SIZE, 1)'
 code = '''
     lfs3_t lfs3;
     lfs3_format(&lfs3, LFS3_F_RDWR, CFG) => 0;