[PROF-11078] Fix profiling exception when agent url is an ipv6 address

**What does this PR do?**

This PR builds atop #4237 and fixes a similar-ish issue in the profiler
caused by the same mishandling of ipv6 addresses.

In particular, when provided with an ipv6 address in the agent url,
the profiler would fail with an exception:

```
$ env DD_AGENT_HOST=2001:db8:1::2 DD_PROFILING_ENABLED=true \
bundle exec ddprofrb exec ruby -e "sleep 2"

dd-trace-rb/lib/datadog/profiling/http_transport.rb:27:in `initialize':
Failed to initialize transport: invalid authority (ArgumentError)
```

**Motivation:**

Luckily we didn't have any customers using this, as it fails immediately
and loudly, but it's still a bug on a configuration that should be
supported.

**Additional Notes:**

Since we had similar buggy logic copy-pasted in crashtracking and
profiling (crashtracking had been fixed in #4237) I chose to extract
out the relevant logic into the `AgentSettings` class, so that
both can reuse it.

**How to test the change?**

I've added unit test coverage for this issue to profiling, and
the snippet above can be used to end-to-end test it's working fine.

Here's how it looks on my machine now:

```
E, [2025-01-02T17:32:32.398756 #359317] ERROR -- datadog: [datadog]
(dd-trace-rb/lib/datadog/profiling/http_transport.rb:68:in `export')
Failed to report profiling data (agent: http://[2001:db8:1::2]:8126/):
failed ddog_prof_Exporter_send: error trying to connect: tcp connect
error: Network is unreachable (os error 101): tcp connect error:
Network is unreachable (os error 101): Network is unreachable (os error 101)
```

E.g. we correctly try to connect to the dummy address, and fail :)

(Note: The error message is a bit ugly AND repeats itself a bit.
That's being tracked separately
in DataDog/libdatadog#283 )

lib/datadog/profiling/http_transport.rb

@@ -13,13 +13,11 @@ class HttpTransport
       def initialize(agent_settings:, site:, api_key:, upload_timeout_seconds:)
         @upload_timeout_milliseconds = (upload_timeout_seconds * 1_000).to_i
 
-        validate_agent_settings(agent_settings)
-
         @exporter_configuration =
           if agentless?(site, api_key)
             [:agentless, site, api_key].freeze
           else
-            [:agent, base_url_from(agent_settings)].freeze
+            [:agent, agent_settings.url].freeze
           end
 
         status, result = validate_exporter(exporter_configuration)
@@ -75,29 +73,6 @@ def export(flush)
 
       private
 
-      def base_url_from(agent_settings)
-        case agent_settings.adapter
-        when Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER
-          "#{agent_settings.ssl ? "https" : "http"}://#{agent_settings.hostname}:#{agent_settings.port}/"
-        when Datadog::Core::Configuration::Ext::Agent::UnixSocket::ADAPTER
-          "unix://#{agent_settings.uds_path}"
-        else
-          raise ArgumentError, "Unexpected adapter: #{agent_settings.adapter}"
-        end
-      end
-
-      def validate_agent_settings(agent_settings)
-        supported_adapters = [
-          Datadog::Core::Configuration::Ext::Agent::UnixSocket::ADAPTER,
-          Datadog::Core::Configuration::Ext::Agent::HTTP::ADAPTER
-        ]
-        unless supported_adapters.include?(agent_settings.adapter)
-          raise ArgumentError,
-            "Unsupported transport configuration for profiling: Adapter #{agent_settings.adapter} " \
-                        " is not supported"
-        end
-      end
-
       def agentless?(site, api_key)
         site && api_key && Core::Environment::VariableHelpers.env_to_bool(Profiling::Ext::ENV_AGENTLESS, false)
       end

sig/datadog/profiling/http_transport.rbs

@@ -19,10 +19,6 @@ module Datadog
 
       private
 
-      def base_url_from: (Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings agent_settings) -> ::String
-
-      def validate_agent_settings: (Datadog::Core::Configuration::AgentSettingsResolver::AgentSettings agent_settings) -> void
-
       def agentless?: (::String? site, ::String? api_key) -> bool
 
       def validate_exporter: (exporter_configuration_array exporter_configuration) -> [:ok | :error, ::String?]

spec/datadog/profiling/http_transport_spec.rb

@@ -127,6 +127,19 @@
           http_transport
         end
       end
+
+      context "when hostname is an ipv6 address" do
+        let(:hostname) { "1234:1234::1" }
+
+        it "provides the correct ipv6 address-safe url to the exporter" do
+          expect(described_class)
+            .to receive(:_native_validate_exporter)
+            .with([:agent, "http://[1234:1234::1]:12345/"])
+            .and_return([:ok, nil])
+
+          http_transport
+        end
+      end
     end
 
     context "when additionally site and api_key are provided" do