Add river online ML package

[BurnySc2]

• Add river package
• Fix poetry version to <2.0.0 because export command has been moved to a poetry plugin

Requirements Changes Report
=========================

New Packages:
------------
river: 0.22.0

[vschmidt91]

Some quick-and-dirty performance results from the ladder.

Setup:

• example river model (1000+ params, see below)
• run 10 training steps per game iteration
• client.game_step = 2

Code

model = (
    pp.StandardScaler() |
    nn.MLPRegressor(
        hidden_dims=(30,),
        activations=(
            nn.activations.ReLU,
            nn.activations.ReLU,
            nn.activations.Identity
        ),
        optimizer=optim.SGD(1e-3),
        seed=42
    )
)

def on_step():

    # ...

    start = time.time()
    for _ in range(10):
        xb = pd.DataFrame(np.random.uniform(size=(10, 100)))
        yb = pd.DataFrame(np.random.uniform(size=(10, 10)))
        y_pred = model.predict_many(xb)
        model.learn_many(xb, yb)

    model.predict_many(xb)
    end = time.time()
    print(f"model training took: {round((end - start) * 1000, 3)}ms")

Results

https://aiarena.net/matches/3538285/
https://aiarena.net/matches/3538286/
https://aiarena.net/matches/3538287/

Average frametime (reported by AIArena): 14-16 ms
Min-Max frametime (measured): 10-20 ms

[lladdy]

Nice, thanks for the writeup @vschmidt91.
Looks good to me.