Use pre-built CI Docker image in doc-build workflow

[stephanosio]

Installing the required packages on the go in a workflow is risky because external dependencies (e.g. a mirror) may go down or decide to purge some files.

For example, https://discord.com/channels/720317445772017664/884782246010175528/971917170281947186

To prevent this, add the required dependencies for thedoc-build workflow in the CI Docker image and use the image in the workflow.

Also, while we are at it, see if there are any other workflows that do this and apply a similar fix.

[stephanosio]

Added to CI Docker image in: zephyrproject-rtos/docker-image#101

[stephanosio]

This can be considered part of #40.