DEV: Add process pid to `bin/turbo_tests --format documentation` output (#22429)

Why this change?

The process's pid is useful when we're trying to link output from
different processes together. In this case, we want to be able to link
the Rails server logs to the right rspec process.

Before:

[2] Viewing sidebar mobile collapses the sidebar when clicking outside of it

After:

[2] (#176342) Viewing sidebar mobile collapses the sidebar when clicking outside of it

lib/turbo_tests/documentation_formatter.rb

@@ -37,7 +37,8 @@ module TurboTests
     private
 
     def output_example(example)
-      output = +"[#{example.process_id}] #{example.full_description}"
+      output =
+        +"[#{example.process_id}] (##{example.metadata[:process_pid]}) #{example.full_description}"
 
       if run_duration_ms = example.metadata[:run_duration_ms]
         output << " (#{run_duration_ms}ms)"

lib/turbo_tests/json_rows_formatter.rb

@@ -55,6 +55,7 @@ module TurboTests
             example.metadata[:shared_group_inclusion_backtrace].map(&method(:stack_frame_to_json)),
           extra_failure_lines: example.metadata[:extra_failure_lines],
           run_duration_ms: example.metadata[:run_duration_ms],
+          process_pid: Process.pid,
         },
         location_rerun_argument: example.location_rerun_argument,
       }