Ensure tests use URI from speedy_stdlib even if Bundler loaded URI

When running through `bundle exec`, Bundler will have loaded URI already
which will make our speedy_stdlib skip redefining it.

Aggressively undefine URI if loaded through Bundler so that our tests
perform against our implementation, not the stdlib one.

test/helper.rb

+if defined?(Bundler) && defined?(URI)
+  Object.send(:remove_const, :URI)
+  $".reject! { |p| p =~ %r{(^|/)uri[/.]} }
+end
+
 require 'minitest/autorun'
 require 'hub'
 

test/speedy_stdlib_test.rb

 require 'helper'
 
 class URITest < Minitest::Test
+  def test_uri_is_from_speedy_stdlib
+    # if it were stdlib, URI::HTTPS would be the result
+    assert_equal URI::HTTP, URI.parse("https://example.com").class
+  end
+
   def test_uri_display_port
     assert_equal "https://example.com", URI.parse("https://example.com").to_s
     assert_equal "https://example.com:80", URI.parse("https://example.com:80").to_s