[otp_ctrl] Dedicated zeroization DAI error bit

Errors during a `ZEROIZE` DAI request result in the same error bits being set
in the `STATUS` register (e.g., `AccessError`) as for the regular `READ`, `WRITE`
or `DIGEST` commands.

Having a dedicated error bit for the `ZEROIZE` command would demarcate errors that
can only occur during a zeroization of a OTP word from the other ones. For example,
for added protection, the DAI could itself check the validity of a zeroized word by
counting the number of set bits and signal an error if the zeroization criterion is not
met (see this [discussion](https://github.com/lowRISC/opentitan/pull/28044#discussion_r2321452250)).

Adding a new error bit to the `STATUS` register has the side-effect of reducing the
maximum number of partitions as their error bits are also held in `STATUS`.
#26746 proposes to separate error and status bits into different registers such
that new error bits can be added more freely.

Start with the otp_ctrl DAI ZEROIZE handling and STATUS register definition. Review the linked discussion and issue #26746 for the register-layout constraints, then verify that ZEROIZE errors are distinguishable from READ, WRITE, and DIGEST errors without overlooking the partition-count impact.

Written by the indexing model from the issue text.