Use a more limited number of threads when fetching in parallel

The currently hardcoded 25 is too much and seems to cause some systems
to even run out of memory.

This also removes the only rubinius specific code in the repository. We
don't really support rubinius so it doesn't make sense to keep those
different branches.

Author: deivid-rodriguez

bundler/lib/bundler/fetcher/compact_index.rb

@@ -116,7 +116,7 @@ def serial_compact_index_client
       def bundle_worker(func = nil)
         @bundle_worker ||= begin
           worker_name = "Compact Index (#{display_uri.host})"
-          Bundler::Worker.new(Bundler.current_ruby.rbx? ? 1 : 25, worker_name, func)
+          Bundler::Worker.new(Bundler.settings.processor_count, worker_name, func)
         end
         @bundle_worker.tap do |worker|
           worker.instance_variable_set(:@func, func) if func

bundler/lib/bundler/installer.rb

@@ -222,14 +222,7 @@ def installation_parallelization(options)
       # Parallelization has some issues on Windows, so it's not yet the default
       return 1 if Gem.win_platform?
 
-      processor_count
-    end
-
-    def processor_count
-      require "etc"
-      Etc.nprocessors
-    rescue StandardError
-      1
+      Bundler.settings.processor_count
     end
 
     def load_plugins

bundler/lib/bundler/settings.rb

@@ -209,6 +209,13 @@ def pretty_values_for(exposed_key)
       locations
     end
 
+    def processor_count
+      require "etc"
+      Etc.nprocessors
+    rescue StandardError
+      1
+    end
+
     # for legacy reasons, in Bundler 2, we do not respect :disable_shared_gems
     def path
       configs.each do |_level, settings|