Initial commit of basic file creation

Currently limited to inlined files and only simpler truncate-writes.

But still this lets us test file creation/deletion.

This is also enough logic to make it clear that, even though we have
some powerful high-level primitives, mapping file operations onto these
is still going to be non-trivial.

runners/bench_runner.c

@@ -1387,6 +1387,8 @@ void perm_run(
         .block_count        = BLOCK_COUNT,
         .block_cycles       = BLOCK_CYCLES,
         .cache_size         = CACHE_SIZE,
+        .inline_size        = INLINE_SIZE,
+        .bud_size           = BUD_SIZE,
         .lookahead_size     = LOOKAHEAD_SIZE,
     };