Fail with exception on timeout while waiting for connection pool

[dennisschroer]

Motivation:

When a timeout occurs while waiting for a new connection, the future fails with a simple "Timeout" message without a stack trace. This makes it very difficult to debug where in the application the error occurs. We have a longer running process with multiple requests to the database, and having a stacktrace would help us.

Conformance:

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Please also make sure you adhere to the code style guidelines: https://github.com/vert-x3/wiki/wiki/Vert.x-code-style-guidelines

[vietj]

can you reproduce this case with a test ? it is not clear how it happens.

I would like this behaviour to be tested and the only case it can happen is when the connection pool is too busy to respond (which shall not happen unless it is blocked) or when there is a race with the acquisition (basically cancel succeeds and returns false, it was not able to cancel because the handler got satisfied which makes the connection borrower progress).

also this callback cannot fail, it is always completed with a succeeded future, unless the pool is closed