(SIMP-7974) Add new GLCI pipeline features

[op-ct]

The patch adds enhanced features to SIMP Puppet modules' standardized GitLab CI pipeline:

• spec and acceptance tests only run when relevant files have changed
• The CI variable SIMP_FULL_MATRIX is replaced by SIMP_MATRIX_LEVEL
• spec and acceptance tests run at or above their SIMP_MATRIX_LEVEL
• Jobs and the pipeline default to SIMP_MATRIX_LEVEL 1
• The pipeline's SIMP_MATRIX_LEVEL can be changed via CI variable (via triggers, group/project settings, etc)
• In the pipeline-triggering commit message, adding a line that starts with CI: MATRIX LEVEL 0 or CI: SKIP MATRIX will suppress all steps with SIMP_MATRIX_LEVEL 1-3

There is an important caveat: because of the way GitLab CI pipelines determine changes, a file that hasn't changed between --amend + force-pushed updates will not trigger the matrix again. This affects scheduled and triggered pipelines.

• To solve this scenario, setting the CI variable SIMP_FORCE_MATRIX = yes in a scheduled pipeline or pipeline trigger will ensure that all jobs at the current SIMP_MATRIX_LEVEL are run, regardless of what has changed (or not).

CI: SKIP_MATRIX SIMP-8035 #close SIMP-7974 #comment Add file-match CI runs to pupmod-simp-pupmod SIMP-7975 #comment Add SIMP_MATRIX_LEVEL checks to pupmod-simp-pupmod