fix: App start definitions for iOS and Android (#15798)

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Corrects the definitions of cold/warm starts

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---------

Co-authored-by: Markus Hintersteiner <markus.hintersteiner@sentry.io>

Author: noahsmartin

docs/concepts/search/searchable-properties/events.mdx

@@ -342,13 +342,13 @@ Returns results with a matching maximum value for the field entered.
 
 ### `measurements.app_start_cold`
 
-A [cold start](/product/insights/mobile/mobile-vitals/app-starts/) refers to when the app launches for the first time after a reboot or update. The app is not in memory and no process exists.
+A [cold start](/product/insights/mobile/mobile-vitals/app-starts/) on Android refers to when the app process is created from scratch. On iOS it is only the first time a process is created after a reboot or update.
 
 - **Type:** duration
 
 ### `measurements.app_start_warm`
 
-A [warm start](/product/insights/mobile/mobile-vitals/app-starts/) refers to when the app has already launched at least once and is partially in memory. For instance, the user backs out of your app, but then re-launches it. The process may have continued to run, but the app must recreate the activity from scratch.
+A [warm start](/product/insights/mobile/mobile-vitals/app-starts/) on Android refers to when the app launches with some saved state, for example it may have an existing process and only need to create a new Activity. On iOS it is any process creation that isn't a cold start.
 
 - **Type:** duration
 

docs/platforms/apple/common/tracing/instrumentation/automatic-instrumentation.mdx

@@ -102,8 +102,8 @@ To enable this feature, enable `enableAutoPerformanceTracing`.
 
 The SDK differentiates between a cold and a warm start, but doesn't track hot starts/resumes.
 
-- **Cold start**: App launched for the first time, after a reboot or update. The app is not in memory and no process exists.
-- **Warm start**: App launched at least once, is partially in memory, and no process exists.
+- **Cold start**: App launched for the first time, after a reboot or update. A cold start begins when the process is created.
+- **Warm start**: Any time the process is created that isn’t a cold start.
 
 <Alert>
 
@@ -118,7 +118,7 @@ The Cocoa SDK creates the following app start spans:
 - **Runtime Init to Pre Main Initializers**: from runtime init to pre main initializers.
 - **UIKit Init**: from pre main initializers to the when starting the Sentry Cocoa SDK.
 - **Application Init**: this reflects the duration of your AppDelegate `application:didFinishLaunchingWithOptions` method or [App conformer's initializer](<https://developer.apple.com/documentation/swiftui/app/main()>) when using SwiftUI, which is from when starting the Cocoa SDK to the [`didFinishLaunchingNotification`][didfinishlaunching].
-- **Initial Frame Render**: from the [`didFinishLaunchingNotification`][didfinishlaunching] until the app renders its first frame. **Starting with version 9.0.0, this is the default behavior.** In versions prior to 9.0.0, this measured until [`UIWindowDidBecomeVisibleNotification`][uiwindow] unless you enabled the `enablePerformanceV2` option.
+- **Initial Frame Render**: from the [`didFinishLaunchingNotification`][didfinishlaunching] until the first CADisplayLink callback. **Starting with version 9.0.0, this is the default behavior.** In versions prior to 9.0.0, this measured until [`UIWindowDidBecomeVisibleNotification`][uiwindow] unless you enabled the `enablePerformanceV2` option.
 
 ![App Start Transaction](./img/app-start-transaction.png)