commitlog/config: Make hard size enforcement false by default + add config opt

Refs #9053

Flips default for commitlog disk footprint hard limit enforcement to off due
to observed latency stalls with stress runs. Instead adds an optional flag
"commitlog_use_hard_size_limit" which can be turned on to in fact do enforce it.

Sort of tape and string fix until we can properly tweak the balance between
cl & sstable flush rate.

Closes #9195

(cherry picked from commit 3633c077be)

db/commitlog/commitlog.cc

@@ -136,6 +136,7 @@ db::commitlog::config db::commitlog::config::from_db_config(const db::config& cf
     c.extensions = &cfg.extensions();
     c.reuse_segments = cfg.commitlog_reuse_segments();
     c.use_o_dsync = cfg.commitlog_use_o_dsync();
+    c.allow_going_over_size_limit = !cfg.commitlog_use_hard_size_limit();
 
     return c;
 }