[PROF-5860] Allow new CPU Profiling 2.0 **alpha** profiler to be enabled

[ivoanjo]

The new Ruby profiler, aka "CPU Profiling 2.0", is considered to be alpha state. We do not recommend turning it on.

But! We actually can turn it on now -- by using DD_PROFILING_FORCE_ENABLE_NEW=true.

The rest of the pieces have been put into place in previous PRs.

What does this PR do?:

Add a setting that allows choosing between the "old" profiler codepath, and the new "CPU Profiling 2.0" codepath.

Motivation:

Making it possible to test the new profiler.

Additional Notes

This PR sits atop #2208 because without the component in #2208 the profiler would not be able to be turned on. It is otherwise independent from that change.

How to test the change?:

Here's a simple run of the new profiler:

$ DD_TRACE_DEBUG=true DD_PROFILING_ENABLED=true DD_SERVICE=ivoanjo-testing DD_ENV=staging DD_PROFILING_FORCE_ENABLE_NEW=true bundle exec ddtracerb exec ruby -e sleep
I, [2022-08-05T14:40:38.715368 #24783]  INFO -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/profiling/tasks/setup.rb:47:in `check_if_cpu_time_profiling_is_supported') CPU time profiling skipped because native CPU time is not supported: Feature requires Linux; macOS is not supported. Profiles containing 'Wall time' data will still be reported.
D, [2022-08-05T14:40:38.727312 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/core/workers/async.rb:133:in `start_worker') Starting thread for: #<Datadog::Core::Telemetry::Heartbeat:0x00007f825b982080>
D, [2022-08-05T14:40:38.727510 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/core/configuration/components.rb:371:in `startup!') Profiling started
D, [2022-08-05T14:40:38.727647 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/profiling/collectors/cpu_and_wall_time_worker.rb:33:in `block in start') Starting thread for: #<Datadog::Profiling::Collectors::CpuAndWallTimeWorker:0x00007f827b91b950>
D, [2022-08-05T14:40:38.727712 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/core/workers/async.rb:133:in `start_worker') Starting thread for: #<Datadog::Profiling::Scheduler:0x00007f826c07bb60>
D, [2022-08-05T14:41:38.735153 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/profiling/stack_recorder.rb:25:in `serialize') Encoded profile covering 2022-08-05T13:40:38Z to 2022-08-05T13:41:38Z
D, [2022-08-05T14:41:40.534027 #24783] DEBUG -- ddtrace: [ddtrace] (dd-trace-rb/lib/datadog/profiling/http_transport.rb:49:in `export') Successfully reported profiling data