chore: Android benchmark screen of SR data pipelines on iOS Raw Frames (#410)

## Summary

Added benchmark to test CPU and compression of session replay data
pipelines


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Changes are isolated to the e2e app and benchmarking utilities plus a
small non-functional formatting tweak in the SDK; primary risk is
increased repo/app size and potential build/runtime impact from the
added benchmark assets.
> 
> **Overview**
> Adds a new in-app **Session Replay benchmark** flow to the Android e2e
app: a `BenchmarkActivity` that loads a recorded Mastodon frame dataset
from assets, runs multiple compression strategies and
`TileSignatureManager` timing, and displays results in a bottom sheet.
> 
> Wires the benchmark into the compose app via a new Manifest activity
entry and a Main screen button, adds the required
`kotlinx-serialization-json` dependency for event encoding, and includes
the benchmark `frames.csv` asset dataset. Minor housekeeping:
`.gitignore` now ignores `lib/.cxx`, and
`ExportDiffManager.createCaptureEvent` is reformatted (no behavioral
change intended).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
7bdef21. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: abelonogov-ld

e2e/android/app/build.gradle.kts

@@ -90,7 +90,7 @@ dependencies {
     // Uncomment to use the publicly released version (note this may be behind branch/main)
     // implementation("com.launchdarkly:launchdarkly-observability-android:0.2.0")
 
-    implementation("com.launchdarkly:launchdarkly-android-client-sdk:5.10.0")
+    implementation("com.launchdarkly:launchdarkly-android-client-sdk")
 
     implementation("io.opentelemetry:opentelemetry-api:1.51.0")
     implementation("io.opentelemetry:opentelemetry-sdk:1.51.0")
@@ -120,6 +120,9 @@ dependencies {
     implementation(platform(libs.androidx.compose.bom))
     implementation("androidx.compose.runtime:runtime")
 
+    // Serialization runtime (used by benchmark to encode replay events)
+    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.8.1")
+
     // Compose UI dependencies -- only for the compose flavor
     "composeImplementation"(libs.androidx.activity.compose)
     "composeImplementation"(libs.androidx.ui)

e2e/android/app/src/compose/AndroidManifest.xml

@@ -15,6 +15,11 @@
         <activity
             android:name=".masking.ComposeWebActivity"
             android:exported="false" />
+        <activity
+            android:name=".benchmark.BenchmarkActivity"
+            android:exported="false"
+            android:label="Benchmark"
+            android:theme="@style/Theme.AndroidObservability" />
 
         <activity
             android:name=".MainActivity"