Revert "[ruby/rubygems] Move bundler/bin scripts to top-level bin/ for simpler test execution"

This reverts commit e98ed19ab0.

spec/bin/bundle

@@ -0,0 +1,6 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "../bundler/support/activate"
+
+load File.expand_path("bundle", Spec::Path.exedir)

spec/bin/parallel_rspec

@@ -0,0 +1,7 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "../bundler/support/setup"
+
+require "turbo_tests"
+TurboTests::CLI.new(ARGV).run

spec/bin/rspec

@@ -0,0 +1,6 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require_relative "../bundler/support/rubygems_ext"
+
+Spec::Rubygems.gem_load("rspec-core", "rspec")

spec/bundler/support/path.rb

@@ -50,7 +50,7 @@ module Spec
     end
 
     def bindir
-      @bindir ||= source_root.join(ruby_core? ? "spec/bin" : "../bin")
+      @bindir ||= source_root.join(ruby_core? ? "spec/bin" : "bin")
     end
 
     def exedir