DEV: Add --profile=[COUNT] option for turbo_rspec

Why is this change required?

By default, `RSpec` comes with a `--profile=[COUNT]` option as well but
enabling that option means that the entire test suite needs to be
executed. This does not work so well for `turbo_rspec` which splits our
test files into various "buckets" for the tests to be executed in
multiple processes. Therefore, this commit adds a similar
`--profile=[COUNT]` option to `turbo_rspec` but will only profile the
tests being executed. Examples:

`LOAD_PLUGINS=1 bin/turbo_rspec --profile plugins/*/spec/system`

or

`LOAD_PLUGINS=1 bin/turbo_rspec --profile=20 plugins/*/spec/system`

lib/turbo_tests/json_rows_formatter.rb

@@ -54,6 +54,7 @@ module TurboTests
           shared_group_inclusion_backtrace:
             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],
         },
         location_rerun_argument: example.location_rerun_argument,
       }