Add task_size parameter to CVAT backend

[ehofesmann]

Resolves #1448

The CVAT REST API imposes a limit on the size of requests. This can cause errors when uploading annotation runs for sample collections with many images or labels to CVAT.

In order to break an annotation run into smaller segments, this PR adds a task_size parameter that limits the number of samples that can be uploaded to a single task in CVAT. Due to the creation of multiple tasks when task_size is provided, we recommend providing a project_name to group the created tasks together.

The task_size parameter can be used in conjunction with segment_size to both define the number of images per task and the number of images per job within the task.

Example

import fiftyone.zoo as foz
import fiftyone as fo

dataset = foz.load_zoo_dataset("quickstart", max_samples=20).clone()

anno_key = "batch_upload"
project_name = "batch_example"

task_size = 6  # 6 images per task
segment_size = 2 # 2 images per job

results = dataset.annotate(
    anno_key,
    label_field="ground_truth",
    task_size=task_size,
    segment_size=segment_size,
    project_name=project_name,
    launch_editor=True,
)

# Annotate in CVAT

dataset.load_annotations(anno_key, cleanup=True)

Note: The CVAT maintainers are working on an update to resolve this issue natively.

[brimoor]

LGTM

[brimoor]

FYI- I moved task_size up here so that it appears near other relevant parameters.

I think this is more user-friendly than strictly adding new kwargs to the end, which makes it harder to grok the available options. This is also why I always recommend using key=value syntax when calling any function with kwargs, so that order can be changed later in cases like this.