[sledge] Add Trace.all

Summary:
This makes it convenient to call

`Trace.init ~margin:70 ~config:all ()`

in test modules.

Reviewed By: mbouaziz

Differential Revision: D14075515

fbshipit-source-id: 3d3940eb1

sledge/src/trace/trace.ml

@@ -20,6 +20,7 @@ type trace_mods_funs = trace_mod_funs Map.M(String).t
 type config = {trace_all: bool; trace_mods_funs: trace_mods_funs}
 
 let none = {trace_all= false; trace_mods_funs= Map.empty (module String)}
+let all = {none with trace_all= true}
 let config : config ref = ref none
 
 let init ?(margin = 300) ~config:c () =

sledge/src/trace/trace.mli

@@ -22,6 +22,7 @@ type config =
         (** Specify tracing of individual toplevel modules *) }
 
 val none : config
+val all : config
 
 val init : ?margin:int -> config:config -> unit -> unit
 (** Initialize the configuration of debug tracing. *)