refactor(cloud): send all end test information in single event

[bernardobridge]

Description

Improves performance of the Cloud testrun:end, which makes the CLI end the test faster.

Pre-merge checklist

This is for use by the Artillery team. Please leave this in if you're contributing to Artillery.

• Does this require an update to the docs? No
• Does this require a changelog entry? Yes

[hassy]

Is there a way we could do this without passing another argument to onShutdown handlers? Would be best to keep the number of arguments those to a minimum as we don't want to encourage using them over beforeExit handlers.

[bernardobridge]

Is there a way we could do this without passing another argument to onShutdown handlers? Would be best to keep the number of arguments those to a minimum as we don't want to encourage using them over beforeExit handlers.

Good shout @hassy! Turns out we already had a mechanism to pass data from beforeExit to onShutdown in the cloud platform, so I can just leverage that: c218de8