feat(amazonq): enable pre flare experiment (#7999)

## Problem


## Solution


---

- Treat all work as PUBLIC. Private `feature/x` branches will not be
squash-merged at release time.
- Your code changes must meet the guidelines in
[CONTRIBUTING.md](https://github.com/aws/aws-toolkit-vscode/blob/master/CONTRIBUTING.md#guidelines).
- License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: andrewyuq

packages/amazonq/src/lsp/client.ts

@@ -21,6 +21,7 @@ import {
 import {
     AuthUtil,
     CodeWhispererSettings,
+    FeatureConfigProvider,
     getSelectedCustomization,
     TelemetryHelper,
     vsCodeState,
@@ -339,12 +340,14 @@ async function onLanguageServerReady(
     // tutorial for inline chat
     const inlineChatTutorialAnnotation = new InlineChatTutorialAnnotation(inlineTutorialAnnotation)
 
-    const enableInlineRollback = true
+    const enableInlineRollback = FeatureConfigProvider.instance.getPreFlareRollbackGroup() === 'treatment'
     if (enableInlineRollback) {
         // use VSC inline
+        getLogger().info('Entering preflare logic')
         await activateInline(client)
     } else {
         // use language server for inline completion
+        getLogger().info('Entering postflare logic')
         const inlineManager = new InlineCompletionManager(client, sessionManager, lineTracker, inlineTutorialAnnotation)
         inlineManager.registerInlineCompletion()
         toDispose.push(

packages/core/src/shared/featureConfig.ts

@@ -39,6 +39,8 @@ export const Features = {
     dataCollectionFeature: 'IDEProjectContextDataCollection',
     projectContextFeature: 'ProjectContextV2',
     workspaceContextFeature: 'WorkspaceContext',
+    preFlareRollbackBIDFeature: 'PreflareRollbackExperiment_BID',
+    preFlareRollbackIDCFeature: 'PreflareRollbackExperiment_IDC',
     test: 'testFeature',
     highlightCommand: 'highlightCommand',
 } as const
@@ -106,6 +108,16 @@ export class FeatureConfigProvider {
         }
     }
 
+    getPreFlareRollbackGroup(): 'control' | 'treatment' | 'default' {
+        const variationBid = this.featureConfigs.get(Features.preFlareRollbackBIDFeature)?.variation
+        const variationIdc = this.featureConfigs.get(Features.preFlareRollbackIDCFeature)?.variation
+        if (variationBid === 'TREATMENT' || variationIdc === 'TREATMENT') {
+            return 'treatment'
+        } else {
+            return 'control'
+        }
+    }
+
     public async listFeatureEvaluations(): Promise<ListFeatureEvaluationsResponse> {
         const profile = AuthUtil.instance.regionProfileManager.activeRegionProfile
         const request: ListFeatureEvaluationsRequest = {