Asynchronous pruning for RubyThreadPoolExecutor #595

Job	Run time
Test without C extension	3m 13s
Test isolated (ruby)	3m 37s
Test isolated (2.3)	1m 46s
Tests: Ruby 2.3 - ubuntu	6m 15s
Tests: Ruby 2.5 - ubuntu	6m 15s
Tests: Ruby 2.4 - ubuntu	6m 17s
Tests: Ruby 2.6 - ubuntu	6m 15s
Tests: Ruby 3.1 - ubuntu	6m 16s
Tests: Ruby 2.7 - ubuntu	6m 16s
Tests: Ruby 3.0 - ubuntu	6m 16s
Tests: Ruby 3.4 - ubuntu	3m 14s
Tests: Ruby truffleruby - ubuntu	4m 19s
Tests: Ruby jruby - ubuntu	5m 12s
Tests: Ruby 3.2 - ubuntu	3m 17s
Tests: Ruby 3.3 - ubuntu	3m 14s
Tests: Ruby ruby - windows	6m 2s
	1h 17m 44s

Provide feedback