Avoid switch statement in particles shader to workaround shader compiler crash on Apple silicon devices

[clayjohn]

Partial cherrypick of #88816 for 4.2 and 4.1. This is the minimum needed to avoid the crash on Apple silicon devices (#72469)

I tested and confirmed that the issue is specifically using a switch statement where the first condition does nothing ¯\_(ツ)_/¯

[YeldhamDev]

Shouldn't there be a comment here (and on master as well) informing why it needs to be done this way?

[clayjohn]

Shouldn't there be a comment here (and on master as well) informing why it needs to be done this way?

Sure!

In practice I'm not sure it matters since we would reject any PR that just changes an if statement to a switch

[akien-mga]

Looks good! I was wondering if we should backport those PRs to 4.2 and 4.1 indeed, a minimal pick like this for Apple devices only sounds great.

[akien-mga]

Thanks!

[Zireael07]

"We would reject any PR that contain a switch" only works as long as you know/remember what and why. A comment is a much more futureproof solution