Update support for passing global_cond to ViT

[sgreenbury]

This pull request adds support for optional global conditioning in the Azula ViT processor and updates relevant configuration files to enable or disable this feature as appropriate. The changes make it possible to pass a global conditioning tensor to the model, with validation to ensure correct usage, and expose this functionality through both the configuration and the processor interface.

Processor enhancements:

• Added global_cond_channels and include_global_cond parameters to the AzulaViTProcessor class and its constructor, allowing the model to be optionally conditioned on a global tensor. [1] [2]
• Updated the forward and map methods to accept and validate a global_cond tensor when global conditioning is enabled, and to pass it to the underlying model. [1] [2]
• Ensured that the model is constructed with the correct global conditioning parameters.

Configuration updates:

• Enabled global conditioning (global_cond_channels: auto, include_global_cond: true) in the large Azula ViT configs for the following experiments: advection_diffusion, conditioned_navier_stokes, gpe_laser_wake_only, and gray_scott. [1] [2] [3] [4]
• Explicitly disabled global conditioning (include_global_cond: false) in the base configs for both large and small Azula ViT processors. [1] [2]