Always generate positive object IDs in inspect

Sometimes, object_ids are created as signed Integers which are invalid
in `inspect`. By using the default implementation of `Object#to_s`, we
can get valid object_ids the same way Ruby itself would have created
them.

For a motivation of this change, see

* https://bugs.ruby-lang.org/issues/13397
* https://github.com/ruby-concurrency/concurrent-ruby/pull/651

lib/rackstash.rb

@@ -47,10 +47,6 @@ module Rackstash
   FIELD_TAGS = 'tags'.freeze
   FIELD_TIMESTAMP = '@timestamp'.freeze
   FIELD_VERSION = '@version'.freeze
-
-  # @!visibility private
-  # we want to look "native" with our inspect values, 7 for 32-bit, 14 for 64-bit
-  DEFAULT_OBJ_ID_STR_WIDTH = 0.size == 4 ? 7 : 14
 end
 
 require 'rackstash/logger'

lib/rackstash/fields/abstract_collection.rb

@@ -38,8 +38,8 @@ module Rackstash
       #
       # @return [String] human-redable details about the object.
       def inspect
-        id_str = (object_id << 1).to_s(16).rjust(DEFAULT_OBJ_ID_STR_WIDTH, '0')
-        "#<#{self.class.name}:0x#{id_str} #{self}>"
+        id_str = Object.instance_method(:to_s).bind(self).call[2..-2]
+        "#<#{id_str} #{self}>"
       end
 
       # Provide a copy of the wrapped {#raw} data in a format allowing direct

lib/rackstash/flows.rb

@@ -81,8 +81,8 @@ module Rackstash
 
     # @return [String] a string representation of `self`
     def inspect
-      id_str = (object_id << 1).to_s(16).rjust(DEFAULT_OBJ_ID_STR_WIDTH, '0')
-      "#<#{self.class.name}:0x#{id_str} #{self}>"
+      id_str = Object.instance_method(:to_s).bind(self).call[2..-2]
+      "#<#{id_str} #{self}>"
     end
 
     # @return [Integer] the number of elements in `self`. May be zero.