Battles: Batch sidebar updates
Battles: Batch sidebar updates

This is the same idea as the statbar batching, but applied to sidebars.
It improves fast-forward performance, and also happens to fix a bug
regarding sidebar updating while fast-forwarding.

Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client