[#171536663] Several pipeline improvements

[raicastino]

The following changes have been implemented to improve the current Azure DevOps pipeline for this repository:

• moved all the build packaging tasks from Build stage (always executed) to Deploy_x stages to accelerate the pipeline execution when deployment is skipped (i.e. not required)
• added templates usage to allow the reuse of several recurrent steps in the pipeline (e.g. install node modules and build, deploy a function, etc.): this improve readability, maintenance and reuse of content, logic, and parameters
• reviewed the conditions and renamed the pipeline variables to support the manual execution of specific jobs on-demand (e.g. allow administrators to execute the deployment of a specified branch or commit in production regardless ‘latest’ tag)
• modified the deployment to slots (optional alternative deployment mode enabled setting appropriate variables) to support deployment slots both in stage and production environment
• improved and added additional comments in the YML pipeline file to better document the pipeline

[gunzip]

lgtm ! very nice !