[host,tools] Allow unsupported `opentitantools` args through `test_args`

During [PR#30966](https://github.com/lowRISC/opentitan/pull/30966), a change was made to support multiple hyperdebug boards (especially FPGAs). Now `test_args` are also passed to the FPGA setup and cleanup phase which are direct calls to `opentitantool` with this flag.

If `test_args` is containing non-recognized arguments for `opentitantool` (may be test harness specific flags), the Setup and Cleanup phase will fail.

__Action__: Find a way to allow or filter unsupported opentitantool options in `test_args`.

The are already some proposals by @pamaury (https://github.com/lowRISC/opentitan/pull/30966#issuecomment-5254397577).

Start with PR#30966 and its discussion, then trace how test_args reach the FPGA setup and cleanup calls to opentitantool. Done means test-harness-specific or otherwise unsupported opentitantool options no longer make setup or cleanup fail, while relevant options continue to work.

Written by the indexing model from the issue text.