[dv] Cleanup Xcelium warning: XProp related
[dv] Cleanup Xcelium warning: XProp related

- Added `-xverbose` elab option by default - this does not impact the
build time significantly.
- Added `xflags` to enable array corruption on invalid / oob index -
suggested by Xcelium

Signed-off-by: Srikrishna Iyer <2803d640feace36379942447842f26c7747b4dc3@google.com>

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