refactor(Dockerfile): optimize Dockerfile structure and layers

[k1lgor]

Improvements

• single layer installation
• no cache with pip
• consolidation of python dependencies
• removal of temp files

As you can see on the image below, the last two builds are with the current state of Dockerfile, and the first two are with the improvements. There is significant build time improvement and slight image size reduction for gpt-researcher image, about 300-400MB. I used docker compose up -d --build.

[assafelovic]

This is great thank you!