Ability to set a global default to ci_extras in ReFrame config #2851
Description
PR #2833 adds the ability to configure the generated child pipelines with arbitrary options using test variable ci_extras. Currently, this variable is defined in the Regression test class and defaulted to an empty dict.
Use case
A very simple use case of this functionality is that the user wants to set a "global" config to ci_extras that will be used in all the tests. With the proposed setup in the PR, the user needs to add this global config inside "each" test. This results in a lot of duplicated code and increase the maintenance burden.
Proposal
Include ci_extras in ReFrame config variable (probably in general) and set the value read from the config file as the default value during the test instantiation and registration. A more generic feature request along the same lines had already been made in #1500