[qemu] QEMU OTP timing modelling fixes

[AlexJones0]

Description

A dependency of #27932.

When running provisioning OpenTitan flows in parallel / on slower devices we run into infrequent OTP timing issues that I have diagnosed to two types:

1. Some OTP checks have quite tight timing checks set and would benefit from shorter OTP delays when running in parallel to pass consistently. In QEMU we should add properties to allow overriding the OTP delays and arbitrarily changing them for given QEMU runs.
2. Under heavy loads, flows that use the OTP (e.g. ROM / ROM-EXT, provisioning) a lot occassionally take significantly longer. This is primarily due to the QEMU Bottom Half being used for digest writes which can be deferred for a longer time than expected under high loads. This should be switched to use a short timer to be able to meet the timing expectations of software.

[AlexJones0]

This was implemented by lowRISC/qemu#310 on the QEMU side which should be pulled in by the next release bump on the OpenTitan side. This means it is not available in OpenTitan yet, but I will close this issue as the QEMU implementation is done and it should be pulled in as a future PR for the QEMU provisioning work.