test(amazonq): add performance test for prepareRepoData (aws#5670)

## Problem
Start of reliability work to enhance performance testing of high risk
code paths.

## Solution
`prepareRepoData` in `src/amazonqFeatureDev/util/files.ts` captures many
potentially high risk paths in a single function, such as `collectFiles`
and other I/O operations, making it a great place to start performance
testing.

Two performance tests were added, one for handling a workspace with many
small files, and one with few large files. Unsurprisingly, the
performance is significantly better on fewer larger files as it reduces
# of I/O operations. Thresholds are very lenient to avoid flaky tests.

The "many files" test does 250 files w/ 10 bytes each. The "large files"
does 10 files w/ 1000 bytes each. These values were chosen to avoid
flakiness in CI.

---

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License: I confirm that my contribution is made under the terms of the
Apache 2.0 license.

Author: Hweinstock

packages/core/src/test/amazonqFeatureDev/prepareRepoData.test.ts

@@ -0,0 +1,73 @@
+/*!
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import assert from 'assert'
+import { WorkspaceFolder } from 'vscode'
+import { performanceTest } from '../../shared/performance/performance'
+import { createTestWorkspace } from '../testUtil'
+import { prepareRepoData, TelemetryHelper } from '../../amazonqFeatureDev'
+import { AmazonqCreateUpload, getRandomString, Metric } from '../../shared'
+
+type resultType = {
+    zipFileBuffer: Buffer
+    zipFileChecksum: string
+}
+
+function performanceTestWrapper(numFiles: number, fileSize: number) {
+    return performanceTest(
+        {
+            testRuns: 10,
+            linux: {
+                userCpuUsage: 100,
+                systemCpuUsage: 35,
+                heapTotal: 4,
+            },
+            darwin: {
+                userCpuUsage: 100,
+                systemCpuUsage: 35,
+                heapTotal: 4,
+            },
+            win32: {
+                userCpuUsage: 100,
+                systemCpuUsage: 35,
+                heapTotal: 4,
+            },
+        },
+        `handles ${numFiles} files of size ${fileSize} bytes`,
+        function () {
+            const telemetry = new TelemetryHelper()
+            return {
+                setup: async () => {
+                    return await createTestWorkspace(numFiles, {
+                        fileNamePrefix: 'file',
+                        fileContent: getRandomString(fileSize),
+                        fileNameSuffix: '.md',
+                    })
+                },
+                execute: async (workspace: WorkspaceFolder) => {
+                    return await prepareRepoData([workspace.uri.fsPath], [workspace], telemetry, {
+                        record: () => {},
+                    } as unknown as Metric<AmazonqCreateUpload>)
+                },
+                verify: async (_w: WorkspaceFolder, result: resultType) => {
+                    verifyResult(result, telemetry, numFiles * fileSize)
+                },
+            }
+        }
+    )
+}
+
+function verifyResult(result: resultType, telemetry: TelemetryHelper, expectedSize: number): void {
+    assert.ok(result)
+    assert.strictEqual(Buffer.isBuffer(result.zipFileBuffer), true)
+    assert.strictEqual(telemetry.repositorySize, expectedSize)
+    assert.strictEqual(result.zipFileChecksum.length, 44)
+}
+
+describe('prepareRepoData', function () {
+    describe('Performance Tests', function () {
+        performanceTestWrapper(250, 10)
+        performanceTestWrapper(10, 1000)
+    })
+})