build: Refactor Dockerfile and local-build script to use build arguments for base image and agent version

[hangy]

Introduces ARG_UBUNTU_BASE_IMAGE, ARG_UBUNTU_BASE_IMAGE_TAG , ARG_TARGETARCH and ARG_VSTS_AGENT_VERSION instead of hardcoding them. Also passes all arguments to the build script to docker build to enable passing additional arguments.

The main idea is that this can allow building a matrix of image variants for different Ubuntu flavours and tags, as well as AzDO agent version and architectures using the same Dockerfile and the same build script.

UBUNTU_BASE_IMAGE=my-ubuntu-image \
    UBUNTU_BASE_IMAGE_TAG=22.04 \
    VSTS_AGENT_VERSION=4.252.0 \
    ./local-build.sh \
    -t example

[btungut]

Dear @hangy ,
Thank you so much for your contribution! Your PR has been reviewed and successfully merged into the master branch.
Looking forward to many more contributions from you!

[hangy]

No, thank you for building this in the first place! :)