Playernames of previous match persist in the next gamesetup

[elexis]

Sometimes we can see playernames of a previous match in the gamesetup.

This error cannot be fixed without deleting the persist-matchsettings or selecting a different maptype.

For years we didn't know how it could occur (so filing this report to have a ticket to find in case we need to look it up again).

But the reason is easy after accidentally finding it in #5199, doubleclicking on Start Game. The first call it will copy over the names, the second call it will save those to the persistmatchsettings file.

There is a different ticket for persist-match-settings saving less information. Playernames should be dropped as well eventually.

[elexis]

Preventing doubleclicks on startGame is important and will be done in ​Phab:D1558.

Cutting the problem at the other root, the ability to save values that don't need saving is to be done in #3883.

[elexis]

In 21843:

Prevent calling the JS gamestart function twice when doubleclicking on the "Start Game" button.

It triggered an OOS on rejoin prior to rP21836, refs #5199 and
resulted in the playernames of the current match persisting into new gamesetups, fixes #5206.

Differential Revision: ​https://code.wildfiregames.com/D1558
Comments By: wraitii