Previously, we would pick an exponent between 0.5 and 2.5, which would
cause a lot of clients to try reconnecting in rapid succession,
overwhelming the server as a result.

This pull request always doubles the previous delay and introduces a
jitter that can, at most, double it.

As part of this, we're also increasing the maximum reconnection delay
from 10s to 30s: this gives us more space to spread out the reconnection
requests.

Release Notes:

- N/A

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Co-authored-by: Marshall Bowers <git@maxdeviant.com>