[PROF-7440] Report status of timeline feature as internal metadata

**What does this PR do?**:

This PR adds support for reporting the status of the timeline feature
together with profiles, via the internal metadata field.

I ended up doing a bunch of refactoring to make it easier to adds new
reported fields as internal metadata; it may be easier to review this
PR commit-by-commit.

**Motivation**:

While this feature is off-by-default, having this internal metadata
makes it easier to spot profiles that have/don't have this data
without actually opening them up in the UX.

**Additional Notes**:

N/A

**How to test the change?**:

This change includes test coverage. It's possible internally at
Datadog to see this information in profile listings (ping me if you'd
like to know more).

lib/datadog/profiling/component.rb

@@ -65,9 +65,11 @@ def self.build_profiler_component(settings:, agent_settings:, optional_tracer:)
         # NOTE: Please update the Initialization section of ProfilingDevelopment.md with any changes to this method
 
         no_signals_workaround_enabled = false
+        timeline_enabled = false
 
         if enable_new_profiler?(settings)
           no_signals_workaround_enabled = no_signals_workaround_enabled?(settings)
+          timeline_enabled = settings.profiling.advanced.experimental_timeline_enabled
 
           recorder = Datadog::Profiling::StackRecorder.new(
             cpu_time_enabled: RUBY_PLATFORM.include?('linux'), # Only supported on Linux currently
@@ -81,7 +83,7 @@ def self.build_profiler_component(settings:, agent_settings:, optional_tracer:)
             gc_profiling_enabled: enable_gc_profiling?(settings),
             allocation_counting_enabled: settings.profiling.advanced.allocation_counting_enabled,
             no_signals_workaround_enabled: no_signals_workaround_enabled,
-            timeline_enabled: settings.profiling.advanced.experimental_timeline_enabled,
+            timeline_enabled: timeline_enabled,
           )
         else
           load_pprof_support
@@ -92,6 +94,7 @@ def self.build_profiler_component(settings:, agent_settings:, optional_tracer:)
 
         internal_metadata = {
           no_signals_workaround_enabled: no_signals_workaround_enabled,
+          timeline_enabled: timeline_enabled,
         }.freeze
 
         exporter = build_profiler_exporter(settings, recorder, internal_metadata: internal_metadata)

spec/datadog/profiling/component_spec.rb

@@ -90,9 +90,16 @@
           build_profiler_component
         end
 
-        it 'sets up the Exporter with no_signals_workaround_enabled: false' do
+        it 'sets up the Exporter internal_metadata with no_signals_workaround_enabled: false, timeline_enabled: false' do
           expect(Datadog::Profiling::Exporter)
-            .to receive(:new).with(hash_including(internal_metadata: { no_signals_workaround_enabled: false }))
+            .to receive(:new).with(
+              hash_including(
+                internal_metadata: {
+                  no_signals_workaround_enabled: false,
+                  timeline_enabled: false,
+                }
+              )
+            )
 
           build_profiler_component
         end
@@ -258,12 +265,19 @@
           build_profiler_component
         end
 
-        it 'sets up the Exporter with no_signals_workaround_enabled setting' do
+        it 'sets up the Exporter internal_metadata with no_signals_workaround_enabled and timeline_enabled settings' do
           allow(Datadog::Profiling::Collectors::CpuAndWallTimeWorker).to receive(:new)
 
           expect(described_class).to receive(:no_signals_workaround_enabled?).and_return(:no_signals_result)
-          expect(Datadog::Profiling::Exporter)
-            .to receive(:new).with(hash_including(internal_metadata: { no_signals_workaround_enabled: :no_signals_result }))
+          expect(settings.profiling.advanced).to receive(:experimental_timeline_enabled).and_return(:timeline_result)
+          expect(Datadog::Profiling::Exporter).to receive(:new).with(
+            hash_including(
+              internal_metadata: {
+                no_signals_workaround_enabled: :no_signals_result,
+                timeline_enabled: :timeline_result,
+              }
+            )
+          )
 
           build_profiler_component
         end