Add thread and ractor counts to bug reports

This is useful for crash triaging. It also helps to hint extension
developers about the misuse of `rb_thread_call_without_gvl()`.

Example:

    $ ./miniruby -e 'Ractor.new{Ractor.receive};
        Thread.new{sleep}; Process.kill:SEGV,Process.pid'
    <snip>
    -- Threading information ---------------------------------------------------
    Total ractor count: 2
    Ruby thread count for this ractor: 2

1 files changed, 3 insertions, 0 deletions

diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 13d720be9e..64d8d93d3f 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -755,6 +755,9 @@ class TestRubyOptions < Test::Unit::TestCase
         )?
       )x,
       %r(
+        (?:--\sThreading(?:.+\n)*\n)?
+      )x,
+      %r(
         (?:--\sMachine(?:.+\n)*\n)?
       )x,
       %r(