[3.x] Fixed texture animation speed when using random lifetime

[RPicster]

3.x version of #55271

[akien-mga]

What about the tex_* parameters in CPUParticles2D? They seem to be initialized to 0 too in 3.x, that's why I thought it might need a deeper dive in the history (and testing) to make sure that everything is working as expected.

[RPicster]

What about the tex_* parameters in CPUParticles2D? They seem to be initialized to 0 too in 3.x, that's why I thought it might need a deeper dive in the history (and testing) to make sure that everything is working as expected.

Oh right! I will take another look, make everything have one style and test it!

[RPicster]

I checked the behaviour of all particle types and the change I did in 4.0 had to be reverted for this PR (changing the tex_* values) because the implementation of the behaviour is different here. Changing those values led to a different default behaviour.

The change was reverted from this PR and now the fix focuses on the animation speed only.

[akien-mga]

Thanks!