fix(okhttp): keep the wrapped EventListener per Call

[markushi]

📜 Description

SentryOkHttpEventListener held the wrapped EventListener in a single mutable field that
callStart overwrote for each call. It is now kept in a per-Call map, the same pattern the class
already uses for eventMap. No public API change.

💡 Motivation and Context

OkHttp uses one listener instance for all calls, thus concurrent calls were all delegated to the
listener made for the call that started last. This breaks the EventListener.Factory contract and
loses the terminal callEnd/callFailed of every overlapping call.

• resolves: SentryOkHttpEventListener breaks EventListener.Factory contract #5967
• resolves: JAVA-695

💚 How did you test it?

Added unit tests.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.
• Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.

🔮 Next steps

[linear-code]

JAVA-695

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.53.0 (1)	release

⚙️ sentry-android Build Distribution Settings