feat!: implement AI Bridge heading to /deployment/observability (#20791)

> [!CAUTION]
> In whichever release this lands, we've removed the ability to provide
keys via a YAML file (specifically on `openai_key`, `anthropic_key`,
`bedrock_access_key` and finally `bedrock_access_key_secret`). This will
need to be described in the release notes as to not break peoples AI
Bridge integrations upgrading from older versions.

This pull-request ensures that we can see the overview of the settings
of the `AI Bridge` feature within the `/deployment/observability` route.
This set of options only render when the `aibridge` feature flag is
enabled.

### Preview


![preview-ai-bridge-observability](https://github.com/user-attachments/assets/262d2456-94b4-49b2-9b4e-b14583e70ede)

codersdk/deployment_test.go

@@ -84,6 +84,20 @@ func TestDeploymentValues_HighlyConfigurable(t *testing.T) {
 		"Notifications: Email Auth: Password": {
 			yaml: true,
 		},
+		// We don't want these to be configurable via YAML because they are secrets.
+		// However, we do want to allow them to be shown in documentation.
+		"AI Bridge OpenAI Key": {
+			yaml: true,
+		},
+		"AI Bridge Anthropic Key": {
+			yaml: true,
+		},
+		"AI Bridge Bedrock Access Key": {
+			yaml: true,
+		},
+		"AI Bridge Bedrock Access Key Secret": {
+			yaml: true,
+		},
 	}
 
 	set := (&codersdk.DeploymentValues{}).Options()