Vendor in latest OpenTitan IPs

[SamuelRiedel]

Update the vendor/lowrisc_ip directory to align Ibex with the latest version of the prims and fusesoc 2.4.3. The current prims were vendored in almost 1.5 years ago.

This PR is currently a work in progress and will require cleanup before merging.

• [x] Include Ibex patches from OpenTitan
• [x] Vendor-in latest OpenTitan prims
• [x] Align Ibex with the new prims
• [x] Update fusesoc to align with OpenTitan's version
• [ ] Check whether the dv/uvm/core_ibex/common/prim can be removed entirely
• [ ] Replace hardcoded filelists with fusesoc output (e.g. dv/uvm/core_ibex/ibex_dv.f)
• [ ] Clean up git history