[dv/aes] Update AES script to support masking and unmasking variant
[dv/aes] Update AES script to support masking and unmasking variant

This PR updates the aes_base_cfg.hjson to support adding a variant:
1). Override the rel_path and scratch_path so masking and unmasking
  version can be in two differet folders.
2). Update test names to include the two variants.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@opentitan.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan