Improve the logic to extract the requestUserId for context objects

[seratch]

While testing this new feauture, I found that the logic to set context.requestUserId can be improved for Events API patterns. I will make changes for it in a different pull request.

As I mentioned at #1144, bolt-java's user ID extration for context objects can be improved like bolt-python does.

Category (place an x in each of the [ ])

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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