Add support for odor mixtures

[bruno-f-cruz]

Each patch can only use a single odor. This can easily change and should be afforded by the schema here:

Aind.Behavior.VrForaging/src/DataSchemas/aind_behavior_vr_foraging/task_logic.py

Line 76 in 1bc757e

class OdorSpecification(BaseModel):

class OdorSpecification(BaseModel):
    index: int = Field(..., ge=0, le=3, description="Index of the odor to be used")
    concentration: float = Field(default=1, ge=0, le=1, description="Concentration of the odor")

one idea would be to do away with the "index" property and simply turn "concentration" into an array where each position of the array sets the concentration of a specific channel.

class OdorSpecification(BaseModel):
    concentration: List[float]