refactor: factor frequently-used run environment variables into getters
A number of variables are defined based on the value of run environment
variables (variables that the test configuration configures and sets in
the `artefacts/run/env` file). There are no helpers to help us keep
track of these and their default values across disjoint scripts, so
let's introduce some!
This introduces getters for the `num_uarts`, `primary_uart`,
`payload_uart` and `ports_script` run environment variables. These were
chosen because we need them in the next patch.
Signed-off-by: Chris Kay <chris.kay@arm.com>
Change-Id: I9ddf6f2fc769e023910652b3a3507f1896f97226
(cherry picked from commit 03ffbe70b82d9d7571fea52201e66945d1b4858d)
7 files changed