migrate Verification Plans from core-v-docs to core-v-verif

Created by: strichmo

Break out ISA-level checks for instructions from core-specific vplans

Note that this is intentionally targetting the master branch as a hotfix. This will be followed up by a merge flow to propagate to appropriate core dev branches.

After this PR is approved and merged I will move to delete the plans from the core-v-docs master branch to avoid confusion and duplication.

Signed-off-by: Steve Richmond Steve.Richmond@silabs.com