fix(crash_dump): Replace crash dump directory with a file

apps/emqx_conf/etc/emqx_conf.conf

@@ -27,12 +27,12 @@ node {
   ## Default: "{{ platform_data_dir }}/"
   data_dir = "{{ platform_data_dir }}/"
 
-  ## Dir of crash dump file.
+  ## Location of crash dump file.
   ##
-  ## @doc node.crash_dump_dir
+  ## @doc node.crash_dump_file
   ## ValueType: Folder
   ## Default: "{{ platform_log_dir }}/"
-  crash_dump_dir = "{{ platform_log_dir }}/"
+  crash_dump_file = "{{ platform_log_dir }}/erl_crash.dump"
 
   ## Global GC Interval.
   ##

apps/emqx_conf/src/emqx_conf_schema.erl

@@ -275,7 +275,7 @@ fields("node") ->
          #{  mapping => "emqx_machine.global_gc_interval"
           ,  default => "15m"
           })}
-    , {"crash_dump_dir",
+    , {"crash_dump_file",
        sc(file(),
           #{ mapping => "vm_args.-env ERL_CRASH_DUMP"
            })}