Trim Dockerfile and make Mongo container name more specific

[TibbersHao]

With recent changes in content registry, we might want to do the similar approach for computing api:

1. There are similar chunks of code in each Dockerfile that could be taken out in order to fasten the building process:

RUN apt-get update && apt-get install -y \
    build-essential \
    wget \
    python3-pip\
    ffmpeg\
    libsm6\
    libxext6

I did an initial quick test by taking out such portion from the front-end and job-manager, and can still build the image properly on a M1 machine. I did not change the one in ml-worker as that one has more packages involved.

2. We may consider to change the container name of mongodb to be more specific, in case we need to have multiple mongo container from different applications.