[ottf] Add file field to test_config_t
[ottf] Add file field to test_config_t

This change adds a new field (`file`) for storing the test file name to
`test_config_t`.

Signed-off-by: Alphan Ulusoy <23b245cc5a07aacf75a9db847b24c67dee1707bf@google.com>

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