Add uniform random scale to ParticleVector2Parameter

[AristurtleDev]

Description

Adds a Uniform flag to ParticleVector2Parameter that, when set with Kind = Random, samples a single float and applies it to both X and Y axes. This guarantees per particle aspect ratio preservation when using random scale on a particle emitter. Without this flag, X and Y are sampled independently, meaning each particle can receive a non square scale even when the min/max range is symmetric.

Related Issues/Tickets

• [Feature Request]: Toggle to make the random for scale maintain an aspect ratio. Ember#26

Changes Made

• ParticleVector2Parameter: added public bool Uniform field (default false); updated the Value getter to sample a single value from the X range and return Vector2(s, s) when Uniform is true and Kind is Random.
• ParticleEffectSerializer: reads the Uniform XML attribute with a default of false; writes it only when true, preserving backward compatibility with existing .ember files.
• ParticleEffectReader / ParticleEffectWriter: same read/write changes for the content pipeline (.xnb) variants.

Checklist

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