overview of build workflows

step 1: this repo contains several build and test workflows. create an overview of what exists and what is in use.
step 2: many repos do not use any of those build workflows. consider module repos only and figure out whether they have workflows that can be centralized or not. from that ideally we can derive a concept for the future. either we do multiple small workflows, or we do few big parametrized workflows. or we dont do workflows.

potential demand:
* build
* build, test
* build, test with coverage (potentially 2 coverage approaches)
* build, test with sanitizers

known problems:
* workflows are not very flexible... should these be actions?

Start by inventorying the build and test workflows in this repository, then inspect module repositories to compare which workflows they use. Document the existing workflows, their flexibility and coverage or sanitizer options, and whether they can be centralized. Done means the overview is complete and includes a supported direction for small workflows, parametrized workflows, or no shared workflows.

Written by the indexing model from the issue text.