Use jinja macros to access the pillar data

There is a lot of duplicate code to fetch data from the pillar, especially due to all the handling of non-existent keys in the pillar.

The objective is to create some jinja macros that can be used to reduce the amount of duplicate code.

See https://jinja.palletsprojects.com/en/2.10.x/templates/#macros

No files or tests are named. Start by locating the repeated pillar lookups and their missing-key handling in the Jinja templates, then read the linked Jinja macro documentation. Done means the shared macros replace the duplicate access logic without changing behavior for existing and missing pillar keys.

Written by the indexing model from the issue text.