Use logical core count for test parallelization

This changes the default number of workers when parallelizing tests to
be based on logical core count instead of physical core count.  This may
provide a performance boost for parallelized tests.

This also reverts rails#50545 in favor of using the default worker count.

Author: jonathanhefner

activesupport/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Use logical core count instead of physical core count to determine the
+    default number of workers when parallelizing tests.
+
+    *Jonathan Hefner*
+
 *   Fix `Time.now/DateTime.now/Date.today' to return results in a system timezone after `#travel_to'.
 
     There is a bug in the current implementation of #travel_to:

activesupport/lib/active_support/test_case.rb

@@ -78,7 +78,7 @@ def test_order
       # number of tests to run is above the +threshold+ param. The default value is
       # 50, and it's configurable via +config.active_support.test_parallelization_threshold+.
       def parallelize(workers: :number_of_processors, with: :processes, threshold: ActiveSupport.test_parallelization_threshold)
-        workers = Concurrent.physical_processor_count if workers == :number_of_processors
+        workers = Concurrent.processor_count if workers == :number_of_processors
         workers = ENV["PARALLEL_WORKERS"].to_i if ENV["PARALLEL_WORKERS"]
 
         Minitest.parallel_executor = ActiveSupport::Testing::ParallelizeExecutor.new(size: workers, with: with, threshold: threshold)

railties/lib/rails/generators/rails/app/templates/github/ci.yml.tt

@@ -110,9 +110,6 @@ jobs:
           ruby-version: .ruby-version
           bundler-cache: true
 
-      - name: Configure parallelization
-        run: echo "PARALLEL_WORKERS=$(nproc)" >> $GITHUB_ENV
-
       - name: Run tests
         env:
           RAILS_ENV: test