Allow enabling legacy profiling transport codepath via setting/env va…

…riable

If needed, this will allow customers to toggle the legacy profiling
transport codepath by setting the
`DD_PROFILING_LEGACY_TRANSPORT_ENABLED` environment varaible to `true`
or by using

```ruby
Datadog.configure do |c|
  c.profiling.advanced.legacy_transport_enabled = true
end
```

As described in the previous commit, this is temporary and only being
added just in case we need to debug issues with the newly-added
`HttpTransport` (or to confirm that an issue did not come from it).

lib/datadog/core/configuration/components.rb

@@ -313,6 +313,18 @@ def build_profiler_collectors(settings, old_recorder, trace_identifiers_helper)
 
           def build_profiler_transport(settings, agent_settings)
             settings.profiling.exporter.transport ||
+              if settings.profiling.advanced.legacy_transport_enabled
+                require 'datadog/profiling/transport/http'
+
+                Datadog.logger.warn('Using legacy profiling transport. Do not use unless instructed to by support.')
+
+                Profiling::Transport::HTTP.default(
+                  agent_settings: agent_settings,
+                  site: settings.site,
+                  api_key: settings.api_key,
+                  profiling_upload_timeout_seconds: settings.profiling.upload.timeout_seconds
+                )
+              end ||
               Profiling::HttpTransport.new(
                 agent_settings: agent_settings,
                 site: settings.site,

lib/datadog/core/configuration/settings.rb

@@ -233,6 +233,13 @@ def initialize(*_)
             # Disable gathering of names and versions of gems in use by the service, used to power grouping and
             # categorization of stack traces.
             option :code_provenance_enabled, default: true
+
+            # Use legacy transport code instead of HttpTransport. Temporarily added for migration to HttpTransport,
+            # and will be removed soon. Do not use unless instructed to by support.
+            option :legacy_transport_enabled do |o|
+              o.default { env_to_bool('DD_PROFILING_LEGACY_TRANSPORT_ENABLED', false) }
+              o.lazy
+            end
           end
 
           # @public_api