[Story] Enforce using the same dotnet versions accross github workflows

[ouphi]

Description

The dotnet version is setup several times in workflows with the following step:

    - uses: actions/setup-dotnet@v3.0.1
      with:
        dotnet-version: '6.0.x'

This story is about implementing a solution to avoid defining the dotnet version in different places in the github workflows.

Solution proposal

A solution would be to create a custom github action that set up the dotnet-version and reuse this action. This custom action would become the placeholder for the dotnet version.

Acceptance criteria

• The dotnet version is only specified once in github actions.