[10.x] Add "Server has gone away" to DetectsLostConnection

[Jubeki]

Closes #51229

[dennisprudlo]

@Jubeki out of curiosity, is case sensitivity necessary here? Would lowercasing the message also be an option or is it better to be explicit in case the same message in a different case means something completely different for some reason?

[driesvints]

Yes casing is important here. See the linked issue.

[dennisprudlo]

@driesvints yes, what I meant was that the fix was necessary because the error message is being transformed to "uppercase the first character" by an sql engine or a hosting provider. If another provider returns the message in say title case or the same provider uses this logic for other messages as well, another update will be necessary.

Can't this be simplified by lowercasing the strings before checking (this wouldn't require redundant messages)? Or is this too risky?

[driesvints]

@dennisprudlo I'm not sure myself. Your idea sounds good to me tbh. We could maybe try it out.