Remove spawn task for each packet.

[XAMPPRocky]

When measured it seems we wasting more time with moving memory into the task than we gained from having it be its own task.

[quilkin-bot]

Build Succeeded 🥳

Build Id: e8704765-b1b7-44c8-94db-ecb2dd8f5e79

The following development images have been built, and will exist for the next 30 days:

• us-docker.pkg.dev/quilkin/ci/quilkin:0.8.0-dev-ed335ca

To build this version:

git fetch git@github.com:googleforgames/quilkin.git pull/842/head:pr_842 && git checkout pr_842
cargo build