Add a @Timeout example for 'poll until' logic

[rmannibucau]

Overview

Proposing a pattern using @timeout for "wait until" like tests.

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[sbrannen]

Tentatively slated for 5.5 GA for team discussion

[sbrannen]

I generally recommend the use of Awaitility for such use cases.

So, if we add an example like this in the User Guide we should also point the users to third-party solutions such as Awaitility.

[sbrannen]

Please make the requested changes and point the users to third-party solutions such as Awaitility.

[sbrannen]

Team Decision: include such content, and we should also point the users to third-party solutions such as Awaitility.

[sbrannen]

in progress: with the intent of fixing the Spotless violation and polishing locally before merging into master

[sbrannen]

This has been merged into master in e6006fe and further refined in 4f2da09.

Thanks for the PR!

In the future, please be mindful of the following.

• Example test classes in the documentation project must have the Demo suffix in order to be included in the build.
• Example test methods must be annotated with @Test.
• Sections in the User Guide require explicit anchors.