Minor: Improve Datadog::Profiling::HttpTransport error logging

**What does this PR do?**:

This PR tweaks the `HttpTransport` error logging to include the
configuration being used.

For instance, it will now look like:

```
ERROR (lib/datadog/profiling/http_transport.rb:58:in `export') Failed to
report profiling data ({:agent=>"unix:///fake-apm-socket.socket"}):
failed ddog_prof_Exporter_send: error trying to connect: No such file
or directory (os error 2): No such file or directory (os error 2)
```

...I did notice the libdatadog error message seems to be repeated and
isn't particularly great; that's a separate issue for a future fix
(on the libdatadog side).

**Motivation**:

While investigating #3037 I noticed this information was not being
logged when the profiler failed to report, and I thought it would be
come in handy when debugging future issues.

**Additional Notes**:

N/A

**How to test the change?**:

The change includes test coverage. You can also manually trigger an
issue by running dd-trace-rb with an invalid configuration, e.g.
the above error message was triggered by running with

```bash
$ DD_PROFILING_ENABLED=true DD_TRACE_AGENT_URL=unix:///fake-apm-socket.socket \
  bundle exec ddtracerb exec ruby -e "sleep 1"
```

lib/datadog/profiling/http_transport.rb

@@ -48,11 +48,14 @@ def export(flush)
             Datadog.logger.debug('Successfully reported profiling data')
             true
           else
-            Datadog.logger.error("Failed to report profiling data: server returned unexpected HTTP #{result} status code")
+            Datadog.logger.error(
+              "Failed to report profiling data (#{config_without_api_key}): " \
+              "server returned unexpected HTTP #{result} status code"
+            )
             false
           end
         else
-          Datadog.logger.error("Failed to report profiling data: #{result}")
+          Datadog.logger.error("Failed to report profiling data (#{config_without_api_key}): #{result}")
           false
         end
       end
@@ -128,6 +131,10 @@ def do_export(
           internal_metadata_json,
         )
       end
+
+      def config_without_api_key
+        [@exporter_configuration[0..1]].to_h
+      end
     end
   end
 end

sig/datadog/profiling/http_transport.rbs

@@ -58,6 +58,8 @@ module Datadog
         Array[[::String, ::String]] tags_as_array,
         ::String internal_metadata_json,
       ) -> [:ok | :error, ::Integer | ::String]
+
+      def config_without_api_key: () -> ::Hash[:agent | :agentless, ::String]
     end
   end
 end

spec/datadog/profiling/http_transport_spec.rb

@@ -222,18 +222,64 @@
     end
 
     context 'when failed' do
-      before do
-        expect(described_class).to receive(:_native_do_export).and_return([:ok, 500])
-        allow(Datadog.logger).to receive(:error)
+      context 'with a http status code' do
+        before do
+          expect(described_class).to receive(:_native_do_export).and_return([:ok, 500])
+          allow(Datadog.logger).to receive(:error)
+        end
+
+        it 'logs an error message' do
+          expect(Datadog.logger).to receive(:error).with(
+            'Failed to report profiling data ({:agent=>"http://192.168.0.1:12345/"}): ' \
+            'server returned unexpected HTTP 500 status code'
+          )
+
+          export
+        end
+
+        it { is_expected.to be false }
       end
 
-      it 'logs an error message' do
-        expect(Datadog.logger).to receive(:error)
+      context 'with a failure without an http status code' do
+        before do
+          expect(described_class).to receive(:_native_do_export).and_return([:error, 'Some error message'])
+          allow(Datadog.logger).to receive(:error)
+        end
 
-        export
+        it 'logs an error message' do
+          expect(Datadog.logger).to receive(:error)
+            .with('Failed to report profiling data ({:agent=>"http://192.168.0.1:12345/"}): Some error message')
+
+          export
+        end
+
+        it { is_expected.to be false }
+      end
+    end
+  end
+
+  describe '#config_without_api_key' do
+    subject(:config_without_api_key) { http_transport.send(:config_without_api_key) }
+
+    context 'when using agentless mode' do
+      let(:site) { 'test.datadoghq.com' }
+      let(:api_key) { SecureRandom.uuid }
+
+      around do |example|
+        ClimateControl.modify('DD_PROFILING_AGENTLESS' => 'true') do
+          example.run
+        end
+      end
+
+      it 'returns the mode and site, but not the api key' do
+        is_expected.to eq(agentless: 'test.datadoghq.com')
       end
+    end
 
-      it { is_expected.to be false }
+    context 'when using agent mode' do
+      it 'returns the mode the agent url' do
+        is_expected.to eq(agent: 'http://192.168.0.1:12345/')
+      end
     end
   end